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Alex #336681 10/05/10 1:40 am
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Hi Ron,

Re

"Sorry guys.. but.. there is only a very limited information available when using an inertia dyno and an O2 sensor.. To get good data you need a brake and a 5 gas analyzer at a minimum, (other data such as a flow meter and EGT add more data as well) otherwise..well not much better than guessing... Inertia dyno's do have their place, but not for true race tuning."

"the numbers are basically bogus..that is well known, they calibrate an inertia dyno on a modern bike... You can use the results to compare when you make a change. "

I think we might be working at cross purposes here.

If you mean to say carburation tuning is best done at stabilised rpm steps on a brake dyno then I agree. I would also note that the inertia dyno I use can be programmed to hold the bike at selected rpms or speeds on a fixed throttle opening. So in fact it can be run as a brake dyno.

But I cant agree with "Inertia dyno's do have their place, but not for true race tuning." if we are talking about developing exhausts, inlet tracts, carb sizes, cam timing and ignition timing.

My own experience is that it is very useful.

I have owned British bikes for 42 years, from the age of 15. But my experience has a huge gap in it. Until I left university I rode bikes every day for transport.I was broke the whole time and had no experience whatsoever of competion or performance tuning.

Roll on 20 years through marriage, kids, career, divorce etc and Im faced with golf or motorcycle racing which is what I wanted to do when I was 15 years old.

But now all the classic bike tuners Im competing against have a 20 year head start!In my first two years I barely finished 5 races and I was as slow as slow. The reliability thing got better one stupid mistake at a time.

But tuning came from reading Vizard, Blair and Bell and going to the dyno to test what they said.

Big steps came from cam tuning, inlet tuning and exhaust tuning.

The first time I went to the dyno 28 bhp rear wheel. Last time over 50 BHP rear wheel - same dyno - same basic engine - only the cam changed and head ported. In less than 5 years I had caught and passed the other tuners. All except the Lodge ES2 bikes which are really really good and come out of an engineering company in Auckland with two generations of car and bike racing experience.

I absolutely could not have done it without the inertia dyno I have used.


The results work on the track too. I have a video of Tony drafting and then pulling out and passing a Manx from a "name" tuner down the back straight of Pukekohe.

In my opinion it is the second best tool in the box. The first best are the books I mentioned above.

John



Last edited by johnm; 10/05/10 2:00 am.
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Alex #336684 10/05/10 1:47 am
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Then why on the 2 strokes would richening up the mix on bottom end and thru the middle make them live? If it was totally all timing which you say it was, the bottom end and middle jetting wouldnt make them live anyway. It was both timing and fuel that caused problems. And there is no way richening up the pilot is gonna help you at the end of the straight. All that will do is make the bike act like a switch when you grab the throttle. Too rich. You would probably yell at me for what i do to a 1 1/2 GP to make it work.


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Alex #336714 10/05/10 7:08 am
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Thanks for posting the graphs Alex, do you know how that compares to the data logger HP? Have you done a dyno run with that lately?
Maybe I can end or add fuel to Ron and Rob's difference of opinion. I'm lazy so I'll leave the carbs as is and check fuel consumpion on my BSA now the timing has been retarded a bit, was idling at about 950RPM now 800 so it's back a bit. I think I know what it will do. And here is a question: why does it idle faster on the same air and presumably fuel with more advance? And why did they put vac advances on cars to adv them when cruising but when you open the throttle they revert to a more retarded setting? I always thought it was for fuel economy?
The best economy I ever had from the BSA was with 38mm lectron carbs because they are very adjustable just off idle, that was around 90miles per imp gallon at 70-80MPH (but could have been running a fair bit of adv)with the 38 TM's I get less than 60.


mark
Alex #336736 10/05/10 10:41 am
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Mark, i believe you are going to lose a little fuel economy if you leave the cards the exact same and just retard it. But the only way to know is try it. May be so small its not measurable. Dont know. What i do know is a pilot jet is not gonna change your main jet airfuel ratio till you maybe get back to the fourth decimal point which is not gonna be the difference between burning a motor down. I think they put the vac advancers on the cars because it leans them out for mileage and when you load the motor it backs it up so it doesnt knock. And wow those lectron carbs got some mileage! Sounds like you have that thing running well! Im getting ready to build a A65 soon... may have to talk to you some!


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Alex #336743 10/05/10 11:28 am
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I have seen something interesting, that may be what Ron is talking about with the pilot jet, I was at eastern creek watching some classics racing and esp watching BSA's and I think it was a particularly nice one of them, a Gold star I think, crossing the line at the end of the race he shut the throttle and the back wheel locked, it was on the straight and it just skidded, and I wondered why it had it's problem then, why not when it was on full noise for 4 or 5 laps? I don't know exactly what went the matter but perhaps it was what Ron speaks of where with the throttle closed without fuel going into it much to cool it it got too much heat suddenly, and that would be where perhaps a bigger pilot jet would let extra fuel keep the temp in it at a livable level on a shut throttle, I think that is what he means?


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Originally Posted by RHall-HCV
Mark, i believe you are going to lose a little fuel economy if you leave the cards the exact same and just retard it. But the only way to know is try it. May be so small its not measurable. Dont know. What i do know is a pilot jet is not gonna change your main jet airfuel ratio till you maybe get back to the fourth decimal point which is not gonna be the difference between burning a motor down. I think they put the vac advancers on the cars because it leans them out for mileage and when you load the motor it backs it up so it doesnt knock. And wow those lectron carbs got some mileage! Sounds like you have that thing running well! Im getting ready to build a A65 soon... may have to talk to you some!
Hey you just get my eight valve head done.:-)You can argue with ron till we are all blue in the face.Going to put Robs head work to good use this weekend. check the results sunday night.LOL I'll bet the tri has fast lap of the weekend ,any bets, Vintage that is.Hate being cocky thats when things go wrong:-)


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Alex #336783 10/05/10 2:28 pm
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Ah you guys are funny... It is very clear you are more interested in "numbers''..

But yes the final dyno is the race track... Tim you don't NEED no stinkin 8 valve head... gotta tie a boat anchor to your back side anyway...!!

Hmm wondering how Barber is gonna turn out...wish I was there...

Cheers..!!

Ron

Alex #336798 10/05/10 4:13 pm
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Hope barber goes well to all. Wish i was going to be there. Always some good competition there. Tim, im waiting on a few experimental peices for the 8 valve... its gonna be good i guess we can see what other parts will break next. haha You have a bottom end ready?? haha


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Originally Posted by Ron - in California
Ah you guys are funny... It is very clear you are more interested in "numbers''..


Cheers..!! I hope that was not directed at me.

Ron
I hope that was not toward me, you know numbers look good on paper but at the end of the day, how did you finish.


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Alex #336808 10/05/10 6:08 pm
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Tim, you have always underestimate your contribution to this. None of this HP talk means anything unless you know the line and keep the throttle on. You more than proved this while campaigning the 500. You would beat 95% of these guys on a B50 with K70's.

Alex #336826 10/05/10 7:20 pm
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Rob, did dad show you the three variants of stock 650 pistons. Notice the difference between them and the 750 short rod?

Alex #336838 10/05/10 9:08 pm
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Yes. Hope I havnt annoyed anyone.

I just think the dyno is a great learning tool especially for people like me without years of experience.

Cheers

John

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Originally Posted by John Healy
Tim, you have always underestimate your contribution to this. None of this HP talk means anything unless you know the line and keep the throttle on. You more than proved this while campaigning the 500. You would beat 95% of these guys on a B50 with K70's.
Well I agree A bike is nothing with out a good rider but a good rider is nothing with out a good bike.:-) what is it thay say ,takes two. Speaking of 500's I would love to get that bike back out. god I loved that thing.


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Alex #336859 10/06/10 12:21 am
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Got it!

Should have said

Best tool - rider
Second best - books
Third best - dyno.

:-)

Hey Tim,

Just agree with my company to do a two year posting in Kazakhstan. Starting early next year. So no racing for me for a while. One day we will get you guys down here. Flights are easy. Enough good bikes are the issue.

Regards

John


Alex #336873 10/06/10 1:44 am
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Yes, you guys have fun this weekend... make sure we get a full report...!! Tim will there be any other FAST Manx's there..? Or are you in a class all by yourself..? Hey... you ARE in a class all by yourself anyway....!!

I wonder if Crank Pin is going..?? Say hello to Roper, he said he was going to be a spectator...

Cheers..!!

Ron

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oh yes Ron, pat will be there and a very fast goldie from canada, very fast and trick.I didn't pre reg so will be on the back row but will make for a fun race:-)Just got off the phone with crank pin and he is on his way soon with maria.Crank pin is riding a manx too, if the crank pin holds up:-)


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Alex #336880 10/06/10 2:23 am
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John, Havnt gotten to look at the pistons yet...Jake was going to bring them to me last weekend but forgot. Dad said he would ship out tomorrow and ill look and send them right back to you. Funny you should say "a B50 on k70's" I have a 570cc B50 on K70's! and it is surprising how well those bikes ride! I out ran one of those Aprilla bikes down a mountain, he couldnt believe it! But i had to go fast...it wont stop! Scared me to death, but a wins a win!


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Alex #336932 10/06/10 2:21 pm
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Tim, darn... just thought about it... should had you get one of those $10.00 DVR to put on the back of your bike... especially since you will have to pass everyone...

I hope Crank Pin's bike survives... he sure looked like a hurt puppy dog up at Miller... as they say... all dressed up and no one to dance with...

Dang... I should be there too... (I have a free airline ticket), but my weekend is destined to be very busy... trying to make the racer a rolling chassis again....

Pictures... lots of pictures....

Cheers..!!

Ron

johnm #336933 10/06/10 2:26 pm
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John, no way man.... keep in mind most of us know each other... we tease and taunt each other unmercifully at times... no harm meant... and sometimes we all learn something...

And I am also sure we all love to hear of the racing going on in other parts of the world... keeps the juices flowing..!!

Cheers..!!

Ron

Originally Posted by johnm
Yes. Hope I havnt annoyed anyone.

I just think the dyno is a great learning tool especially for people like me without years of experience.

Cheers

John

Alex #337011 10/07/10 12:22 am
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All good. Sometimes I worry. You cannot see the smile on people's faces though a computer.

I certainly wind up my mates down here. Inter make rivalry.

My friends own and race Velos. Extremely good bikes. I attend Velo rallies but I have never owned one. I say Im allowed in because I have pushed them for hundreds of miles.

Cheers

John


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' Shutting the throttle totally cuts both the mixture and the air, and when the rpm's are up as they are when racing, the internal heat can go sky high.. especially when the ignition timing is at max. A lot of racers run a larger pilot jet, than would be used on a street bike.'

Many years ago in Australia there was a guy called Eric Walsh who had a BSA Bantam which would do 100mph. He also identified the role of the pilot jet in stopping seizures after the throttle is slammed shut.


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My brother and I are involved in racing H1 and H2 Kawasaki sidecars on speedway using methanol. We use standard timing and compression and bore the mikuni jets. It is sometimes necessary to counter bore the needle jet to avoid the situation where the tip of the needle obstructs the flow at full throttle. If this happens you can fit all the bigger size main jets you like, you won't richen the mixture.


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My brother Douglas Cotterell from Melbourne Australia:
[Linked Image]


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From GS Ron's post:

"The single that burns down after so many miles...do you think that is more of a heat cycle related thing? As if its getting so hot the piston gets softer after each run, to the point of galling on the cylinder thus creating more heat and melting?

"No, your air cooled engine cools by air flow (both externally and internally) and with fuel (some engines use the oil to aid in cooling).. close the throttle partially off of the main jet, and you have another test condition for mixture. Shutting the throttle totally cuts both the mixture and the air, and when the rpm's are up as they are when racing, the internal heat can go sky high.. especially when the ignition timing is at max. A lot of racers run a larger pilot jet, than would be used on a street bike."

Ok, old boring story for you...but I am in agreement with Ron on the low speed jetting on a race bike.

In the 70's, Bultaco built the best out of the box flat track bike money could buy. The 360 Astro virtually over night made a whole lot of novice class and expert class short track bikes obsolete. Being a Bultaco, it was a 2 stroke. And being the AMA, rules got changed to make the novices switch to 250's.

Bultaco developed a "kit" motor to help out all of the owners of 360 Astros. The kit motor consisted of a different cylinder, head, pipe, carb, etc to convert a 360. Very quickly, the 250 "kit" motors got a reputation as being VERY fragile, namely siezure at the end of a straight away when closing the throttle.

The 360's used an AMAL Concentric. The kit motors used a Mikuni. Most people blamed the carb.

By the early 80's, Buls were essentially extinct in the novice class. Only those of us who didn't know better, refused to run a Jap motor, or couldn't afford anything else persisted with a Bul. That description fit a friend of mine & myself WELL.

We persisted with trying to make a 250 Bul kit motor work. We changed heads, ignitions, pipes, etc. We kept getting better, especially after switching from the single plug Motoplat ignition back to a dual plug Femsatronic. Different timing, different advance curve. But it wasn't cured We finally got a handle on the problem when we removed the Mikuni carb, installed a 360 intake manifold, and used a 1036 Concentric.

Now the Astro only siezed once in a while. I learned some tricks about "porting" a piston to get fuel/oil on the cylinder wall and an incorrect pilot jet fixed the problem once and for all.

We ran several Astro's with the same set up. They were fast and reliable. Each one had a stupidly rich pilot jet and slide cutaway. Made it a bit tough for the rider to keep the engine cleared out on the line, but the reliability (and speed) more than made up for some extra attention required from the rider.

As long as the bikes had the "correct" pilot jet and slide cutaway, they went too lean and heat went up WAY too fast inside the engine at the end of a straight away on a half mile. It only took a few laps to hear the death rattle of a Bul siezure (yes, you could hear them rattle before they siezed) Wiseco pistons would last even less time than a Mahle piston.

Being slobbering rich at idle, the fuel/oil would at least carry away some excess heat, at least enough to survive a weekend of racing (we some times did 3 half miles in one weekend) We also found the internals of the engine actually would last longer, pistons lived for what seemed like months, big ends and main bearings would last a season of racing. And we had Buls, with the right rider, running up front.

And about every other weekend, got threatened with a teardown for being illegal eek . No one ever followed through, but heard that threat way too often. Could have used the money grin Most people thought we were running 360's against the 250's. But in some outlaw races we ran one summer, our 250's were faster than the 360 Buls eek

Once we switched to 4 strokes for the junior class (Yamaha, Triumph, & HD), they all were jetted fat at low end. Never had a top end failure in any of the 4 strokes. Actually had very few issues with wearing out bits in the top ends like some people did with the 750's, especially with the restrictor plate motors we had to run in the junior class.

Told you it was a long, boring story grin But I am still believe that for a racing motor, being a bit rich on the idle circuit is a good thing......



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Originally Posted by acotrel
My brother and I are involved in racing H1 and H2 Kawasaki sidecars on speedway using methanol. We use standard timing and compression and bore the mikuni jets. It is sometimes necessary to counter bore the needle jet to avoid the situation where the tip of the needle obstructs the flow at full throttle. If this happens you can fit all the bigger size main jets you like, you won't richen the mixture.


Good point.
I ran mine at the dyno, A10. Got more hp the more fuel I got it. But then suddenly it stopped increasing but didn´t show any lees either. I tried it one more time without a main jet. Got the same number as with one. So the needle jet certainly plays a role and too bad that was the biggest needle jet I had. It´s a couple yres ago and the engine has been apart since. Top end rebuild.

Got 34 at the wheel with my basic 10,5:1 cr, 357 cam, AMAL carb build. Aiming for more when I get it up and running again. But should equal about 40 hp at the engine which is not bad for a basic home build, oh yes a port job was done to the heads to btw.

On the vacuum ignition for cars deal I think that leaning out cruise gives better mpg. BUT leaner mixtures burn slower and therefore need more timing to compensate. That´s where the vacuum comes in. And alot of timing at cruise would also in itself allow for lower throttle openings while getting the same amount of anergy/hp so yes, increasing timing at cruise alone even with fat mixtures would also more efficient.


As for timing having an effect on mixtures, if i´d have to take a guess I would think that when timing is spot on, that would give the highest amount of vacuum allowing more air/fuel in to the combustion chamber. As air is lighter than fuel more air would flow into the chambers with the ignition spot on than with a poorly set ignition. This is kind of vague I know, but would think this has something to do with vacuum and that air is lighter to move than fuel, and since ignition would effect vacuum, this has to be the reason it is doing so. I might have my thinking confused though, with what´s increasing what LOL





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