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Perhaps I should be on the competition board but I thought I'd query the BSA collective first.

The Hornet Race bike Transmission (67 frame and a 71 motor) has left me High and Dry for two races now and i'm am unhappy.

What is going on: The transmission is dragging in neutral. I miss diagnosed the problem as the wrong shim on the layshaft but what I think is happening is gear(s) are push down the shaft toward the primary side and loading the shim on the primary side. I can feel something slipping which I thought was the Newby jumping a tooth but I think its in the transmission. As soon as I feel the slip in WOT I know that soon the bike will be dragging down on power.

When I remove the shim the rear wheel spins freely so when last I was there we machined a shim that would allow the wheel to spin freely. After one lap at Little Taledega today the bike is dragging again and now I cannot find CR2nd and CR3rd. Things are obviously out of position and STD1st and STD4th gears does not a race bike make.

I'm also running a Bob Newby Clutch and the SRM outrigger bearing. Fellow racer Mike Baker suggests I find the spec of where the fixed gears are supposed to be along the Lay Shaft and I can see the wisdom in that but I am worried that I am going to walk the gears around again in race conditions and end up with dragging and miss shifts. So any advise on how to accurately trouble shoot and attack this problem would be greatly appreciated.

Thanks in Advance.
SG - resting at wits end.

Last edited by Semper Gumby; 09/05/21 9:07 pm.
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Not familiar with belt drives but setting up the a65 box property is a fair procedure.
Make sure all the bearings and bushes are in good nick.
Make sure the outrigger is true to the mainshaft run for a start.
Make sure the camplate is in good condition and is the late type. Ditto the plunger
some people remove the point on the plunger end, a good idea. Some people
polish the cam plates and remove all the burrs, a good idea. Some people
shim the camplate in the end housing, a good idea.
Ditto with forks.
Setup and set layshft endfloat..
Although it's difficult to do, check the need for either moving the mainshaft or shimming
the top gear. This really involves some trial and error and fine measuring of gear
engagement etc, bit of a pig to do without having a cutaway box but does pay off.
As a sidecar racer for some years using these old lumps, i went through the learning
curves of a65 gearboxes, they are a crap box but can be made reasonable with loads
of time and patience.

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By the way, why did you bother using a close 3rd?
The only time they are any use is on about one circuit in 100.
Close 1st and 2nd are the ones to have. With GOOD dogs.

Last edited by NickL; 09/05/21 11:13 pm.
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You can weld the selector tracks if shimming doesn't get full engagement on all gears, and a ball ended plunger is good. But it sounds like a problem I've not had and I think you should look at everything it could possibly be.

We had a broken battery terminal that at low rpm felt like the transmission was jamming when it was low voltage to the ignition, the fixed terminal fixed the transmission that we thought was at fault. I think it was retarding or something felt like the brakes were on, and we suspected the transmission.

I think it freed up at rpm when the alternator put in enough voltage, but we thought the trans was trying to lockup at low rpm.

You can set the G/box up and check it out of the bike.

Last edited by Mark Parker; 09/05/21 11:36 pm.

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make sure the shafts are straight, check them for run out between centres .
Do what nick says , particularly the advice on ratios, close 1st and 2nd, std 3rd.

Your set up std 1st, close 2nd , close 3rd is not great, the gap between 2nd and 3rd is too much.


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Interesting.

Time to get the box out on the bench then...Thanks Nick.

As to selection of std Vs.cr gears I don't yet feel qualified to comment yet...

Last edited by Semper Gumby; 09/06/21 2:21 am.
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Getting off the line for short races is talked about in the US quite a bit. I don't know if std 1st addresses that effectively because I've never tried it, but we use 20-40 with C/r 1st on a 750 And 20-38 on another C/r with 17" wheel, and neither take much to get going, or probably more to the point is once they get on the boil a straight should sort out who goes in front anyway? Getting good drive after you get away would be what I'd concentrate on, you still need to get away smartly without breaking anything, but a harder drive will soon round you up.

Wide gaps between high gears does people no favours. I watched video of Phantom's lovely Triumph with a big std 4-5th gap up a long straight, shifting into it meant bikes just keeping with him came past every lap, Kawasaki triple I think. That 4-5th gap is far bigger than a std BSA 3rd and 4th which is very good. Quaife made an A65 5speed with worse ratios than the 4 speed, big gap to top like the Triumph? Getting it right like the PES box helps the motor at every change. I think the C/r BSA 3rd was for 500s at Daytona trying to keep near peak power. I think the PES 4th is near that but with an extra gear and 1st is a little lower than the C/r 1st because it's spread over 5. The C/r 1st and 2nd make the 4speed very nice. But the taper on the main-shaft isn't great.

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A bit fiddly would be an understatement but this sounds like a 'new' problem. I found that the outrigger plate can be tricky to set up. The fit has to be perfect otherwise it will drag. Since we use a dry clutch I found that no plate works fine on the 'gas' bike. Admittedly, we do not have to make hundreds of gearchanges like you guys do. I have used both cr and std on it. With careful shimming they have worked well. The 'fuel' bike uses a carefully set up out rigger and has the dogs undercut. This has been relatively trouble free for many years. Keep us posted! PRT

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I think the cr v std debate is not really the issue that needs to be addressed at this point. Bill takes the disappointment at the track well but if he can't get this bike sorted soon I fear my friend throwing in the towel. With the rear wheel raised bike in neutral, grabbing and turning the wheel feels like lifting weights. Much resistance. When he told me that it was fixed by grinding a shim smaller I knew it was not a true fix. Shims do not grow. I have known Triumph gearboxes where press fit gears have "migrated" on the shafts. Is it possible that could happen to a A65 causing a clearance to tighten up? Are there specs/ measurements of where gears should be on shaft? Something has moved, that much is obvious. Most likely scenario?
Thanks from a racer that would like to see a BSA finish a weekend without drama.

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I'll start another thread on the CR Vs Std ratio gears later. I do want to visit that topic - it was a complete surprise! Right now I'm more concerned with starting and finishing races.

In the early days of this bike I had a stock clutch and chain which ment I had a Cush drive.

NickL - could this be part of my problem. The Newby and the outrigger have no Cush drive which may be hard on the box. I got away with this on the Thunderbolt (not a racer) I think because with the QPD belt drive I didn't have the out rigger bearing. So the flexing main shaft with the belt acted as a "cush" drive?

I'm not at all adverse to going back to the stock clutch and chain as I am quite comfortable keeping the the chain oiled properly now. Its only those cursed rollers that make it such a pain. Is there a chain basket with a one piece roller bearing so I could have a cush drive again?

OR putting on a cush drive rear wheel (and having to machine bits to get it to align).

Taking the day off. Transmission comes out tomorrow.

Last edited by Semper Gumby; 09/06/21 2:36 pm.
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Going on right now. This is all moot until I get the transmission out and see what is going on but....

https://www.britbike.com/forums/ubbthreads.php/topics/846199/1

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I have a Yamaha that will jump out of low gear , and the back wheel turns hard like in two gears at the same time. I’m sure you’ve already checked , but possibly a shifting fork is bent?


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Thanks K. Not yet but Yes. Tomorrow will check all that.

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Originally Posted by Semper Gumby
As soon as I feel the slip in WOT I know that soon the bike will be dragging down on power.

if the gearbox is consuming so much power at WOT then it must heat up considerably. all energy not delivered at the rear wheel is turned into heat in the gearbox. as these components aren't very big they'll heat up. so if this happens again I would check the gearbox oil temperature and see what readings you get.

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It seems like one of the fixed gears has moved on a shaft, if this is the case, then you need to find out why , there shouldnt be side loads on the gears if they all line up properly, i dont think the belt drive / newby clutch has anything to do with it.

i fitted an outrigger when I put in the 5 speed , same as Marks, havent had any issues with it, I did add a few more screws, and fitted them all with studlock.

possibly the sleeve gear bush is tight that would give drag in neutral.It would be OK in 4th when its direct drive,, and get more draggy in the lower gears.


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Originally Posted by gavin eisler
It seems like one of the fixed gears has moved on a shaft, if this is the case, then you need to find out why , there shouldnt be side loads on the gears if they all line up properly, i dont think the belt drive / newby clutch has anything to do with it.

i fitted an outrigger when I put in the 5 speed , same as Marks, havent had any issues with it, I did add a few more screws, and fitted them all with studlock.

possibly the sleeve gear bush is tight that would give drag in neutral.It would be OK in 4th when its direct drive,, and get more draggy in the lower gears.

+1

I’d treat the slipping in top as a separate issue. When I bought my 3rd clutch off Bob I discussed the need for the race clutch on my 823 over the standard clutch with the 5 plate conversion (3x thinner plates) he said there was no difference and I believe him. I have a race clutch also, wider belt etc. The standard clutch with 5 plates has taken a hammering, it’s been tested in the attempt to break it… it won’t. The only
Time it’s slipped is when the clutch nut hasn’t held up to the job and loosened off, then sheered the key and spun on the shaft. The same nut covered over 10,000 miles under my ownership and it wasn’t a new nut.

……….…………


If the box selects neutral better when the thinner shim is at the drive side of the box then there cannot be good alignment with the gears and the selector forks within the cam plate.

You “should” use the thinnest shim only on the timing side of the layshaft, then shim accordingly on the drive side until you have the smallest amount of play. Too much play and the box will jump out of gear.

However, it might be worth fitting the next size shim up on the timing side then shim to suit on the drive side and try again.

A cut away box would be nice, but you would have to shim that box accordingly also. (Least you would on the drive side)


Now let’s all have a beer beerchug

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As lemans said, drag creates heat, something is bent? , shafts or selector forks or both, what was the lay shaft end float on assembly?
Caveat , I could be totally wrong. A bearing perhaps, I could come over and help , but it would take a while.

Last edited by gavin eisler; 09/07/21 10:11 pm.

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The beauty of these gearboxes is that they are a cassette. They can be inspected out of the case. Assuming you shim end float out of the lay shaft hold it and check gear engagement, the sliding gear may not go right in both ways so you can weld a track and file it to get it. But you problem is bigger than that so look closely at everything. Everything around the belt as well.


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Wow. What a day... OK - the Layshaft is straight. I forgot to check the main shaft - will check tomorrow.

OK riddle me this because this is what I found.

The only CR gears in the box are the 2nd gear set - every thing else is Standard. This is a surprise because what I had asked for was CR 2nd and 3rd with STD 1st and of course STD 4th.

But what had been done was the 2nd gear set was in the 3rd gear position and the 3rd gear set was in the 2nd gear position. These gears were switched to the opposite shafts to work. So 2nd gears were matched to each other but were on opposite shafts. Same with the 3rd gears. So I sort of had a Close ratio 2nd and 3rd but I don't know exactly what the Maths are for this. It hurts my brain just typing this.

So you will all be happy to know that I now have the STD 3rd in the correct position and the CR2nd in the correct position.

I don't know if this will fix the layshaft top gear popping off the the primary side of the layshaft or not (I suspect this will happen again but who knows until you twist the wrist?)

So now I have STD 1st CR 2nd STD 3rd and STD 4th which is pretty close to what you all said I should have anyway!

Y'all heard of anything like this before other than the wrong gears got put on the wrong shafts when the main shaft timing side bearing got replaced?

Oh and I have new shift forks in place. And I am getting real good at assembling a transmission and installing. I cannot tell you how many times I counted teeth on gears today but after the first hour I was mumbling unintelligible stuff that sounded like numbers. When I caught a look at the other mechanic in the room, he had a crooked smile on his face suggesting he rather enjoyed watching someone else doing this.


Question: How much should the end float be on the Layshaft?

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Sounds like an attempt at a cheap solution. I think you now have a good starting point. Like others, I'll suggest that you now need the CR 1st set. Rabers or Morrie's Place had CR gears recently. Dont remember which way around it was though, but worth checking.

When I swapped out my STD for CR second I requested the same clearance between the pressed on gear and the freely rotating captured gear (2nd gear?) that is on the layshaft (#34 & #35 in parts book diagram). Might be worth checking that clearance. It wasnt much but would need to be there. I'd have to look back into my notes to see what it was. I think you are saying that the resistance is there hot, so could it be loss of clearance there as the gears get hot? If no resistance when cold that would support that. The question might also be how fixed are the pressed on gears on the shaft, because if knocked sideways there might be some binding?

Good luck. I think others have provided good guidance. Starting from a known point is always good.

Regards


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Hi BB. Thanks. Yes the Layshaft top gear and second gear have clearance between them. It wasn't physically possible to make them bind together.

Another vote for CR 1st! There is a formula in the workshop Manual. Time to do Maths to see what you guys are talking about...

But if I do CR 1st I'll be left on the line by everybody (those Triumph guys) unless I drop the size of the Counter shaft sprocket. Then I will loose top speed?

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layshaft endfloat should be " just perceptible" ~ 0.003".


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Virtually no end float on the lay shaft. Just perceptible.

What gearing are you running? Are you allowed to use 34mm carbs?

I cannot see why mixing the gear pairs would do what you describe unless they are miss matched but that would be a bit hard to put together.

The lay shaft top gear should not move nor have reason to move. What pushes it? Was that big diameter sliding gear in the 3rd position on the main shaft pushing it? But it's only 23t instead of 22t isn't it and should not get it? It's only 2mm bigger? Can 3rd lay shaft gear push it?


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Yes Mark. The SECOND gear could push the layshaft Top - but why?

If the dogs on the sliding layshaft Third were worn (rounded) and not sharp then it could push a bit if it didn't go cleanly into the second gear?

Is there somebody who can re weld the dogs and make them sharp again? Heat treat or Nitritde?



There is somebody I must call...

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The gears are induction hardened, once the dogs have rounded off you have gone through that so need to get it done again.
You'll be lucky if they stay the same size and don't need re-finishing.

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Originally Posted by NickL
The gears are induction hardened, once the dogs have rounded off you have gone through that so need to get it done again.
You'll be lucky if they stay the same size and don't need re-finishing.

By switching the gears back to their proper places I'm using the sharp edges that haven't been worn. So hopefully 'Good Enough" for Barber. After Barber I have somebody who can back cut the dogs and heat treat again. He answered the call...

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What was causing the binding though? And the non selection?


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Putting a rake on the male dogs is easy enough, the females are a bit of a pain
to say the least. Don't go bananas with the angle, may be worth asking John Hill what he used.

Give the bloke who's doing the job the 2 shafts so he can make sure the gears still
slide nicely after heat treatment. (i bet they don't!) He'll probably end up using a
stone to finish the buggers on the splines.

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Nickl - 10 degrees

Mark - I think its the angle on the sliding gear dogs LS 2nd gear forcing the LS 3rd gear into the top gear. The first to second gear would overshoot and start to pull out. The the angle on the dogs would take over. Wear on the bent shift forks probably didn't help either.

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Hi

I think you want to give "Barber" a miss and sort your engine out, your scatter gun approach to your issues is pretty hard to follow. There have been plenty helpful suggestion to your possible problem and methods of assemble.
I'd suggest you fix your crank float before to start with before you junk the motor. Fix the crank float them move on the the G/B. If the gearbox is dragging to the extent you say, then there will be signs inside showing heat and wear to give you and indication where to look first.
If you have a junk timing side casing, cut the crank area off and section the gearbox area, this will allow you to assemble the G/B and see what's going on in there, you'll learn a lot (yes I know all G/B layshaft shimming is different with each casing).
If your 4th L/S gear is being pushed off the shaft, then the shaft is worn.
One or two degrees is all you'll need to back cut the gears.
As Nick said it takes time and patience to get these boxes working good.

My tuppence worth

John

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10 degs? hmm i tried 8 and that was too much really. The gears didn't last long but then
i didn't have them re-hardened. Gearchanges were noticeably heavier and slower but my box was
turning about 20% faster than standard.
I would have thought 5 may be more like it.

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To be on the same page:

[Linked Image from i.postimg.cc]

The drive is through the main shaft, and for 123 it drives the lay shaft that drives the main 4th gear attached to the sprocket, the sliding gear on the lay shaft engages 1st N or 2nd, Ist through the 1st gears with the sliding gear locking it to spin the shaft. 2nd locks the 2nd spinning gear to drive from the main shaft sliding gear on its spline, selecting 3rd slides the gear into 3rd driving through the lay shaft sliding. Top just locks the main shaft to the output gear and sprocket.

With the lay shaft pushed into the carrier you should be able to check all the engagements except top and it should be in the correct spot when you put the cluster in anyway.


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JER.Hill - The crank is fixed on the timing side with the roller bearing conversion so it "floats" on the primary side. The belt drive pulley is up against the splines and not shims against the primary side roller bearing.. I would think a primary chain in this set up would be prone to high wear while a belt would simply move back and forth across the clutch basket as it self centers on the front pulley. Hence my desire to have Dave M's KTM clutch with its Cush drive. I see only benefits to having a Cush drive in the system. But maybe I'm wrong about this... The end of this may be I go back to the timing side bush, lock the crank to the primary side as originally designed and re-install the stock chain and clutch and its Cush drive.

Race bike requires a track to sort but you are correct. There is a track north of Atlanta I can check into before Barber.

Nick - Noted thank you.

Mark - it's a really simple box. I can now hold the thing in my hand, move the selector plate and watch the shift forks push each gear into place. Somehow strangely reassuring. The funny thing is the cost cutting of BSA making the 2nd and 3rd gears the same size in the STD box and thus reversible (for when the dogs get rounded on one side) creating the large jump between 2nd and 3rd which in the mountains is so useless. It forced other compromises on the engine that made it to be merely ordinary - all in the name of cost savings.

Last edited by Semper Gumby; 09/10/21 2:58 pm.
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Are you using a roller for the timing side/ or is it a combi roller and ball ?, if the latter, then end float is sorted, if the former you may like to consider an additional ball bearing mounted to an outrigger plate outboard of the stator, see mark parkers motor, this will capture the crank , stiffen the drive train and nix any endfloat issues, allowing use of chain or belt.

here are the tooth counts i used in 2002 for close first and second, std 3rd and top

mainshaft 4 - 23, 3 - 26, 2 - 22, 1 - 16

layshaft, 4 - 17, 3 - 22, 2 - 25, 1- 24

This give the following ratios,
1st 2.029
2nd 1.471
3rd 1.145
4th 1

With stock CR options this is the best compromise i can come up with for a four speed, on 21 /47 gearing, clutch slip is needed to around 15 mph
once underway there are no big gaps.

std 1st with close ratio 2nd will get you off the line OK, but you will fall into a hole on the change to 2nd.

Close 1st and 2nd will give a little delay off the line but far more thrust once underway.

Also many have found that the CR 1,2 stock 3 , 4 , seems to give a sweeter change

Last edited by gavin eisler; 09/10/21 4:35 pm.

71 Devimead, John Hill, John Holmes A65 750
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Gavin - It's a Combi Roller and Ball. I would like it to be roller only...

Thanks for the ratio numbers.

Last edited by Semper Gumby; 09/10/21 4:50 pm.
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if its a combi ball roller, you should not have end float problems on the primary side, the crank is located at the timing side, apart from a little thermal expansion the primary drive sprocket is fixed axially. Devimead pioneered use of the combi bearing , my self and others have used it with no problems for decades, it does need careful setting up, but once done its pretty much fit and forget. I had to replace my TS combi not beacause of wear, if it wasnt for a small spot of condensation damage I would still be using the original Devi bearing fitted in the early 70s. i only changed it out because the motor was apart and I noticed one rust dot the size of a full stop.


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The stock gears have no rake/angle on the dogs, the twisting motion of the
shafts is what pushes them out of selection The shafts bow with the transmitted torque.
You are relying on the dog engagement and the camplate/selector forks to hold the gears
together. That's why shimming and getting full location is so important with these boxes.
A slight rake on the dogs will make the change slower but if you can live with that it will
improve matters. Too much cut angle will prevent high speed gear change and will knock
the dogs out more quickly. Getting the hardening right will not be easy, you could have
a stock gear tested first and try it at that.
The simple solution for your endfloat problem is to just use a ball race on the drive side.
That's all i have in the 750 race outfit i prepare at the moment, it won't live as long as a
roller but unless you plan to do the TT every month it'll be fine for a couple of years.

The engine is far from ordinary, it won more sidecar races in Europe and the UK than any
other back then, just put together well. Chris Vincent, Peter Brown etc never even used
an end feed setup, nearly all the troubles were with gearboxes not being able to handle
the power they were getting from the a65 engine. I used to push and beat 1200cc honda
4's with my old crate, you wouldn't have got a triumph twin to come anywhere near. we tested
a 650 at a meeting a few weeks ago up against an 840 triumph and a 920 Norton, both had
5 speeds and both ran on methanol, Won 3 races out of 6. Not bad for a 650 eh?

Last edited by NickL; 09/11/21 4:48 am.
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This is with Gavin's close 1 and 2 with a std box, this has the slick ball ended plunger and you can tell riding it. It swaps gears very sweetly and the whole thing is quite smooth. If you go in 47seconds he takes off slow from a roll because drag starts are pretty hard on stuff. I don't know if he uses the clutch, it's not really necessary. But into that 2nd gear and it pulls, it's maybe hard to appreciate the drive in that gear and speed it's picking up. It's running 20-38t but on a 17" wheel similar to 20-40 on an 18. I've used 8500 on one in second but this sounds like he's shifting earlier maybe.

If 2nd doesn't haul someone back I'd be surprised. And we can always do a better head. Which we are going to try because 34mm ports and carbs are flowing about the same as the 38mm version like this has, and more port speed is more hp right through it seems. That changes what you need for gears which are really to keep it in power, changes just take time.

A stock 650 even with a blistering start would be overhauled by the change out of 1st. They are hardly comparable. The tall gears gives the motor something to push against. I think some drag racers do not use first because of that, they probably use wheel spin though.



A main bearing NKIS30 This is from China std clearance $13au each but he had to buy five. Mowers and stuff I work on from the US have Chinese bearings so I expect it's good.

[Linked Image from i.postimg.cc]

Last edited by Mark Parker; 09/11/21 4:43 am.

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There's some stuff i will buy from china and some i won't, bearings are on the the list of won't.
The japs had to buy the companies to find out how to make the steel etc. Maybe in 10 years.......
Same with chains and a few other things.

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Hi Semper

Right. I understand now what you are referring to as "float", you are referring to work expansion. The timing side combo Brg is fine, you do not have to do anything to the crankshaft, so you can cut this from the conversation.
Now what you are identifying to us, is that your drive pulley is locking out on the crank spline and not against the inner race of the roller Brg as it should be.
Changing from the combi Brg back to bush is a none starter and just giving your self way more work.

What you need to do is determine your issues and concentrate on correcting them.
1) Inspect your pulley, spacers and identify all components are correct and shim to correct.
2) Pull the G/B, find and address the issues found, reassemble correctly.
3) Assemble the clutch and check/correct alignment as necessary.
Focus on what your issues are and correct, not jump around all over the place.

my tuppence worth

John

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Originally Posted by gavin eisler
Are you using a roller for the timing side/ or is it a combi roller and ball ?, if the latter, then end float is sorted, if the former you may like to consider an additional ball bearing mounted to an outrigger plate outboard of the stator, see mark parkers motor, this will capture the crank , stiffen the drive train and nix any endfloat issues, allowing use of chain or belt.

here are the tooth counts i used in 2002 for close first and second, std 3rd and top

mainshaft 4 - 23, 3 - 26, 2 - 22, 1 - 16

layshaft, 4 - 17, 3 - 22, 2 - 25, 1- 24

This give the following ratios,
1st 2.029
2nd 1.471
3rd 1.145
4th 1

With stock CR options this is the best compromise i can come up with for a four speed, on 21 /47 gearing, clutch slip is needed to around 15 mph
once underway there are no big gaps.

std 1st with close ratio 2nd will get you off the line OK, but you will fall into a hole on the change to 2nd.

Close 1st and 2nd will give a little delay off the line but far more thrust once underway.

Also many have found that the CR 1,2 stock 3 , 4 , seems to give a sweeter change


Mainshaft 2nd should be 23t.

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Ah, you are correct Nick , well spotted, my notes were wrong. I will edit the original post.


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There is no edit option? Oh well.


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