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Re: Cam timing question with A65 750 [Re: Mark Parker] #752288
10/11/18 9:01 am
10/11/18 9:01 am
Joined: Apr 2005
Posts: 2,458
Bega NSW Australia
Mark Parker Offline OP
BritBike Forum member
Mark Parker  Offline OP
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Joined: Apr 2005
Posts: 2,458
Bega NSW Australia
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
10/11/18 1:41 pm
Joined: Apr 2005
Posts: 2,458
Bega NSW Australia
Mark Parker Offline OP
BritBike Forum member
Mark Parker  Offline OP
BritBike Forum member

Joined: Apr 2005
Posts: 2,458
Bega NSW Australia
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
10/12/18 9:37 am
Joined: May 2013
Posts: 5,557
West Yorkshire
Allan Gill Offline

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Allan Gill  Offline

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Posts: 5,557
West Yorkshire
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
10/12/18 9:48 am
Joined: Apr 2005
Posts: 2,458
Bega NSW Australia
Mark Parker Offline OP
BritBike Forum member
Mark Parker  Offline OP
BritBike Forum member

Joined: Apr 2005
Posts: 2,458
Bega NSW Australia
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
10/12/18 11:13 pm
Joined: Oct 2012
Posts: 4,525
State of absurdity
Hillbilly bike Online content
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Hillbilly bike  Online Content
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Joined: Oct 2012
Posts: 4,525
State of absurdity
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


"Don't be alarmed ladies and gentlemen, these chains are made of chrome steel" Carl Denham, 1932 ...
Re: Cam timing question with A65 750 [Re: JER.Hill] #753103
10/17/18 10:30 am
10/17/18 10:30 am
Joined: Apr 2005
Posts: 2,458
Bega NSW Australia
Mark Parker Offline OP
BritBike Forum member
Mark Parker  Offline OP
BritBike Forum member

Joined: Apr 2005
Posts: 2,458
Bega NSW Australia
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
10/17/18 6:22 pm
Joined: Aug 2001
Posts: 4,593
argyll. scotland, uk
gavin eisler Online content
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gavin eisler  Online Content
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Joined: Aug 2001
Posts: 4,593
argyll. scotland, uk
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
MZ TS 250
The poster formerly known as Pod
Re: Cam timing question with A65 750 [Re: Mark Parker] #753217
10/18/18 1:31 am
10/18/18 1:31 am
Joined: Apr 2005
Posts: 2,458
Bega NSW Australia
Mark Parker Offline OP
BritBike Forum member
Mark Parker  Offline OP
BritBike Forum member

Joined: Apr 2005
Posts: 2,458
Bega NSW Australia
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
10/25/18 11:37 am
Joined: Apr 2005
Posts: 2,458
Bega NSW Australia
Mark Parker Offline OP
BritBike Forum member
Mark Parker  Offline OP
BritBike Forum member

Joined: Apr 2005
Posts: 2,458
Bega NSW Australia
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
11/18/18 6:35 am
Joined: Apr 2005
Posts: 2,458
Bega NSW Australia
Mark Parker Offline OP
BritBike Forum member
Mark Parker  Offline OP
BritBike Forum member

Joined: Apr 2005
Posts: 2,458
Bega NSW Australia
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
11/18/18 11:01 am
Joined: Aug 2001
Posts: 4,593
argyll. scotland, uk
gavin eisler Online content
BritBike Forum member
gavin eisler  Online Content
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Joined: Aug 2001
Posts: 4,593
argyll. scotland, uk
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
The poster formerly known as Pod
Re: Cam timing question with A65 750 [Re: Mark Parker] #756478
11/18/18 1:18 pm
11/18/18 1:18 pm
Joined: Apr 2005
Posts: 2,458
Bega NSW Australia
Mark Parker Offline OP
BritBike Forum member
Mark Parker  Offline OP
BritBike Forum member

Joined: Apr 2005
Posts: 2,458
Bega NSW Australia
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
11/18/18 4:39 pm
Joined: Aug 2001
Posts: 452
Iowa
konon Offline

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konon  Offline

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Joined: Aug 2001
Posts: 452
Iowa
Glad you got it worked out Mark. Is the bike lighter than a stock BSA?


1968 BSA Firebird
1200 HD
XS 1100
1972 Rickman 125
Re: Cam timing question with A65 750 [Re: Mark Parker] #756513
11/18/18 9:21 pm
11/18/18 9:21 pm
Joined: Apr 2005
Posts: 2,458
Bega NSW Australia
Mark Parker Offline OP
BritBike Forum member
Mark Parker  Offline OP
BritBike Forum member

Joined: Apr 2005
Posts: 2,458
Bega NSW Australia
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
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