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Re: Cam timing question with A65 750 [Re: Mark Parker] #752288 10/11/18 9:01 am
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Mark Parker Online Content OP
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Still not right, has a missfire. Might check and ensure there are no air leaks in the intake rubbers or manifold joints or balance tube,

https://www.youtube.com/watch?v=PYSaYt51WNg&feature=youtu.be


mark
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Re: Cam timing question with A65 750 [Re: Mark Parker] #752320 10/11/18 1:41 pm
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Mark Parker Online Content OP
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The DC CDI I posted was what he got. These make things much easier:

https://www.aliexpress.com/item/CDI...ml?shortkey=zMbuyQNb&addresstype=600

I've ordered some trigger/pulse coils that should be easier to mount on the points plate. I'll give an update when I get them. They should be more accurate I think when face down. Triggers are further out and lass disturbed if it wobbles being on a flat plane. I have pulse coils mounted outside the points plate area on the 883, having them on a moveable plate would be much easier for adjusting timing. We never tried adjusting timing with the 883 on the dyno, and it's quite possible that where its set is not optimum. If I have a moveable points plate I can see incremental adjustment, pulling the rotor and moving it makes it more difficult. As does not having a hole in the primary cover.


mark
Re: Cam timing question with A65 750 [Re: Mark Parker] #752425 10/12/18 9:37 am
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Allan Gill Online Happy
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Is it still possible that the cam is too lumpy for the capacity of the motor?

I always remember the twin carb A50 that ma friend had, with a 473 lightning cam it went like S**T off a shovel, but I find them quite tame on the A65, there was nothing special about that A50 either. Also (and probably mentioned earlier) that I had retarded a 473 cam on my lightning so that the lobe centres were equal, (I cant remember the values, but they could have both had an LCA of about 105 for inlet and exhaust) the bike went well, accellerated a treat and top end was good too, but somewhere in the middle about 4000 RPM it was flat, completely flat!! wouldn't accelerate for anything, and this was over a 1000RPM window, a better coil improved it and gave it a 500RPM window but still a pain in the butt having the change to a lower gear, to rev it to a point where I could drop it back in above the flat spot.

If your cam allows it, you could advance the cam a tooth, or with a modified pinion, half a tooth (8 degrees) without clipping the valves on the crowns. but if the over lap is too much, for how ever well flowing the head is (it'll only pull in 375cc per cylinder) are you loosing vacuum (dynamic pressure) becasue the overlap is too much, so your not pulling as much fuel/Air through as you need?

All that said I never did work out why the lightning cam in that position was poor at those revs, advanced from that it was fine, and either side of that flat spot it went like stink....


beerchug
Re: Cam timing question with A65 750 [Re: Mark Parker] #752427 10/12/18 9:48 am
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When you retard them you are relying on gas speed forcing the mixture in past the later shutting inlet valve as the piston is coming up, so exhaust and ports and I imagine compression all play a part in what happens when. Generally the slightly later shutting inlet enhances top end, but really that's minor compared to what can be done with the head and ports.


mark
Re: Cam timing question with A65 750 [Re: Allan Gill] #752515 10/12/18 11:13 pm
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Hillbilly bike Online Content
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Originally Posted by Allan Gill
Is it still possible that the cam is too lumpy for the capacity of the motor?

I always remember the twin carb A50 that ma friend had, with a 473 lightning cam it went like S**T off a shovel, but I find them quite tame on the A65, there was nothing special about that A50 either. Also (and probably mentioned earlier) that I had retarded a 473 cam on my lightning so that the lobe centres were equal, (I cant remember the values, but they could have both had an LCA of about 105 for inlet and exhaust) the bike went well, accellerated a treat and top end was good too, but somewhere in the middle about 4000 RPM it was flat, completely flat!! wouldn't accelerate for anything, and this was over a 1000RPM window, a better coil improved it and gave it a 500RPM window but still a pain in the butt having the change to a lower gear, to rev it to a point where I could drop it back in above the flat spot.

If your cam allows it, you could advance the cam a tooth, or with a modified pinion, half a tooth (8 degrees) without clipping the valves on the crowns. but if the over lap is too much, for how ever well flowing the head is (it'll only pull in 375cc per cylinder) are you loosing vacuum (dynamic pressure) becasue the overlap is too much, so your not pulling as much fuel/Air through as you need?

All that said I never did work out why the lightning cam in that position was poor at those revs, advanced from that it was fine, and either side of that flat spot it went like stink....


Reversion flat spot...sometimes it can be remedied somewhat with exhaust tuning...I have found on Triumphs and a Norton, longer exhaust length, as in long mufflers, can worsen reversion. On a Trident with a huge flat spot from a aftermarket header, a one inch balance pipe between the pipes about a foot from the head completely eliminated reversion for a slight loss at top end..There are other factors at play like intake length, carb mixture and obviously cam timing and I believe the shape of the piston dome in hemi head Brit engines


79 T140D, 96 900M Ducati ,2001 Sportster....On a bike you can out run the demons..
Re: Cam timing question with A65 750 [Re: JER.Hill] #753103 10/17/18 10:30 am
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John, these trigger pulse coils seem the go. I cut the right angled mounting pieces off and drilled mounting holes in the flat part left either side. I'm making an alloy points plate which needs two 20mm holes for the things to sit down in, the wiring terminals will be on the outside hanging over the points plate which on the BSA motors doesn't matter. It's simple to make, they need spacers or bosses under the mounting screws. I should be able to fire the Honda ign with them or try the DC CDI.


https://www.aliexpress.com/item/In-...tml?spm=a2g0s.9042311.0.0.62174c4dvNs96s


mark
Re: Cam timing question with A65 750 [Re: Mark Parker] #753152 10/17/18 6:22 pm
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Thanks for posting this stuff Mark, these coils are amazingly small. Who would have thought? I used to believe size was everything with coils, sjust another thing i had wrong.


71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
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Re: Cam timing question with A65 750 [Re: Mark Parker] #753217 10/18/18 1:31 am
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Thanks for explaining that Nick, I will let you know how it goes.


This is just the trigger system which will work with my honda ign as well and it fits nicely on the points plate.


[Linked Image]

two bolt heads to pulse them, to mimic crank triggering, so the advance works properly.

[Linked Image]

How it fits.

[Linked Image]


I'll cut a big hole in the plate so I can see the bolt heads and get a feeler gauge in to set the clearance.


mark
Re: Cam timing question with A65 750 [Re: Mark Parker] #753957 10/25/18 11:37 am
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It idles fine, spits out the carbs and stumbles driving off, unless you use a few rpm, above that smooth and ultra responsive. Ignition seems fine. Might do some miles on it and see if it becomes more apparent. Once it has a few rpm, throttle off and back on doesn't seem to have any bad areas only low rpm with load. Lower geared than mine with 20-38 sprockets.

https://www.youtube.com/watch?v=wS_dwydbMqM


mark
Re: Cam timing question with A65 750 [Re: Mark Parker] #756459 11/18/18 6:35 am
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So I fixed the carb issues by fitting the above trigger plate to Ben's bike, just started and ran normally with no misfire nor spitting back, changed back to std carb settings, slides etc, std needles were too lean though and switched back to richer needles and it's great. One of the previous trigger coils was likely causing our problems. The only new problem was end float in the idler gear, about .020" which changed the air gap on the triggers, at kick start speed giving no spark, but would push start and run ok.


I made a little bearing housing with a ball race pressed onto the old auto adv centre plate we use as a trigger rotor, the trigger coil plate/(replaces the points plate,) pushes against the nearing housing and eliminates the end float. I could then set the air gap so kick starting gives a spark. There is no sign of reversion or flat spots up to 6000 or a little more. Just good drivable power that starts building progressively from 2500 with serious zoom by 5000. I doubt the clutch is going to cope, it's only 3 spring. It has packer plates and heavy race springs which I will try winding in a bit more, I don't think its particularly slipping yet but feels close.




mark
Re: Cam timing question with A65 750 [Re: Mark Parker] #756468 11/18/18 11:01 am
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gavin eisler Online Content
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Good job Mark , my 3 spring clutch is working V well with the 7 plate conversion and 650 springs.


71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
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Re: Cam timing question with A65 750 [Re: Mark Parker] #756478 11/18/18 1:18 pm
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I have the 7 plate conversion in mine, definitely very good. Ben's has std plates, as many as will go in, plus the heavy springs. His brother Michael took it for a brief ride this afternoon, we could hear him for quite a while, it sounds like a big block V8 Mike is used to an RSV 1000, he thinks the motor is great, but the clutch isn't coping with the power, it may just need a bit more spring pressure. It's weird that they use the type of screws in the pressure plate, they are hard to fit and engage the thread without pushing the bike over, I made ones with hexes on them and more thread for mine so I can just use a socket which is so much easier.


The motor is really nice, it's virtually the same as the 883 with a shorter stroke, it hasn't got the outright torque of the 883 which is around 73lbft but it should approach similar power at higher rpm. If the torque is proportional to the displacement it should make 60lbft which would be 6lbft better than a Z900. And even if hp was proportional to displacement, (and it's not, it's more proportional to breathing) it would equal the Z900s 81hp, however it should do more than that. Why this little motor is so exciting.


mark
Re: Cam timing question with A65 750 [Re: Mark Parker] #756486 11/18/18 4:39 pm
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Glad you got it worked out Mark. Is the bike lighter than a stock BSA?


1968 BSA Firebird
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Re: Cam timing question with A65 750 [Re: Mark Parker] #756513 11/18/18 9:21 pm
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It's a bit lighter, the big difference is the suspension and brakes and weight distribution, tyres, it copes better with rough roads and is like its on rails. The boys are keen to get some good video of it. I'll share it when they do.


mark
Re: Cam timing question with A65 750 [Re: Mark Parker] #781081 08/10/19 7:32 am
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Fitted a gage and wide band sensor for air fuel ratio because the carbs were being very difficult to sort out. It's now 12.5-1 on the main jets at least to a bit over 7000.

[Linked Image from i.postimg.cc]

[Linked Image from i.postimg.cc]

The thing cost around $200 and it makes sorting the carbs extremely easy. The gage is very responsive. We still need to fine tune the low speed circuits. It's amazing to see how the mixture can vary as it progresses through the various circuits. Not something that you could tell by looking at plugs. The thing is smooth and fast, it feels much like the 883 when it zooms. I think it would be very interesting to run it on the dyno. Which would also let us optimize the ign advance. It should make power to 9000 and it would be nice to see how much.

This has only around 10-1 compression when up to 12-1 would be possible, even so it wouldn't surprise me if it didn't make more power than the factory's F750 Triples.

The two little CDIs seem to be working good.


mark
Re: Cam timing question with A65 750 [Re: Mark Parker] #781380 08/13/19 3:03 pm
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I can see my self thinking about this more seriously for mine, I’ve had my pipes ceramic coated so won’t be welding any bungs into them. Might make another set of Siamese, I already have the bungs.

Mines running rich at points but without seeing it coming from the exhaust it’s hard to tell when riding as the bike just continues to pull and take throttle without hesitation.

Are you at 12.5:1 throughout the whole throttle range?


beerchug
Re: Cam timing question with A65 750 [Re: Mark Parker] #781442 08/14/19 9:54 am
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No just on mains, I want it closer to 14.7 on light throttle but still trying to work out why its rich down there then lean then ok. It runs good but probably uses more fuel cruising then necessary. We can see where its rich and lean so will try to correct it. It looks like the needle is the right taper but the tapper seems to start too late, why it goes lean, putting it on the richest clip helps but then its too rich when opened up. There are other needles but they do not give specs, like when the tapper starts and how much tapper there is. There are 4 needles for the 38s, we have 2 varieties and I can measure them with a mic. Tapper on one starts 2mm earlier but is too sharp and too rich by about 1/2 throttle.


mark
Re: Cam timing question with A65 750 [Re: Mark Parker] #781523 08/15/19 11:35 am
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If mains are happy, maybe a smaller needle jet? That has the most effect at very low throttle openings. Cheers, PRT

Re: Cam timing question with A65 750 [Re: Mark Parker] #781532 08/15/19 1:19 pm
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Mark, I had installed an air fuel meter on my Triumph 750 and the O2 sensor was in about the same location as the one I see on your pipes.Mine uses a 2 into one pipe.I was tuning Mikuni TM flatslides with no reliable information to use as a guide..Many expereinced tuners with a history of building winning race engines, told me the O2 senor should be locactd much closer to the exhaust valve, like 12 inches...And gauge readings may not be be absolutley accurate so you need to make other observations..
When the jetting was sorted out I got about 13.8-14,1 indicated fuel/air mixture at part throttle ...The engine response and cafeful examamtion of the sparkplugs with an otoscope indicated it was good....I aslo observed the mufler had a big influence and what seemed correct, was not..


79 T140D, 96 900M Ducati ,2001 Sportster....On a bike you can out run the demons..
Re: Cam timing question with A65 750 [Re: Mark Parker] #781590 08/15/19 10:56 pm
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Tom I tried a smaller needle jet and it allowed the mixture screws to be turned richer by quite a bit, and idle mixture and fractionally above were good but opening the throttle sent it to 19-20-1 and stalled the motor. Maybe the pilot jets are still too big?

Hillbilly the instructions said 2ft from head plus it has a led that indicates if the sensor is too hot or cold in the exhaust flow so its working fine. The thing runs very nice around 13.7-14-1 it just has the dodgey area around idle and just off idle. Rich and then lean and then good,


mark
Re: Cam timing question with A65 750 [Re: Mark Parker] #782265 08/22/19 9:12 pm
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"And gauge readings may not be be absolutley accurate so you need to make other observations.."

Spark plug temp or exhaust gas temp maybe?

perhaps the varying mixture readings are caused by an enrichening effect when the slide is moving up, this will lean out as a steady state is reached at a fixed throttle. I believe Amals do this, probably other carbs work the same way. Hard to watch a constantly changing digital number for this sort of effect , a needle would be a better gauge.


71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: Cam timing question with A65 750 [Re: gavin eisler] #782321 08/23/19 12:39 pm
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Originally Posted by gavin eisler


perhaps the varying mixture readings are caused by an enrichening effect when the slide is moving up, this will lean out as a steady state is reached at a fixed throttle.



This would make sense if there was a leaning off of the mixture as the throttle opens, until the pressure has equalised under the slide (not such a problem on flat slides) and in the port there will be a greater flow of air compared to the negative pressure on the carb jets (leaning the mixture) when this equalises the mixture will richen.


beerchug
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