Help please my BSA 441 has a problem revving

Helllo, i have a BSA 441 "Desert Sled"(see it in my profile), it has a Boyer Ignition, Podtronics rectifier/zener diode replacement, and ive tried three different carbs on it(2 Amals, a 32mm and a 34mm, and a custom billet pumper carb). The problem is it will idle fine, but if you give it any gas it starts to sputter and stumble until you let off the gas. BUT, if you crack open the throttle, and quickly put your hand over the intake and then take it away(to choke it down momentarily), it will rev up fine for a second, then start sputtering again.

Anyone have any ideas? Im thinking maybe the ignition coil is bad or something, but i honestly have no clue.:lol:

thanks

<EDIT>When its idleing it runs really smooth and sounds fine. it only has problems when you rev it.

Its odd that it would do the same thing with three different carbs because what youre describing sounds like a lean pilot circuit.

Are you getting good fuel flow out of the fuel lines?

Does it have a mechanical advance mechanisim on the points still? (still have points?)

Check the mechanical advance for function. And overall timing too...

Have you checked the fual tank for crap or maybe even water contamination?

Check and make sure the fuel tank cap is vented properly sometimes they will hold a vacumm in the tank and disallow fuel flow to the carb.This happened on one of our A65's.Or it could be ignition timing.If it's on the retard side to far they will crap out and almost get a 2 stroke like banging in the exhaust.The other thing is what kind of cam does it stock or radical cam.A hot cam will effect the carburation.

Is the boyer ignition good? Also is the zener diode regulating the voltage correctly?

Its odd that it would do the same thing with three different carbs because what youre describing sounds like a lean pilot circuit.

>when i rev it and it starts cutting out, it smokes and smells really rich.

Are you getting good fuel flow out of the fuel lines?,

>Yes

Does it have a mechanical advance mechanisim on the points still? (still have points?)

>No, it has the spinning magnet thing from the Boyer system(no moving parts)

Check the mechanical advance for function. And overall timing too...

>Havnt done that yet, but its wierd that it ides soo smooth.

Have you checked the fual tank for crap or maybe even water contamination?,

>Yes, its clean and the lines are clear, fuel flows freely through the filter and hose.

Check and make sure the fuel tank cap is vented properly sometimes they will hold a vacumm in the tank and disallow fuel flow to the carb.This happened on one of our A65's.Or it could be ignition timing.If it's on the retard side to far they will crap out and almost get a 2 stroke like banging in the exhaust.The other thing is what kind of cam does it stock or radical cam.A hot cam will effect the carburation.

>I truied revving it with the cap open, made no difference. Again, wouldn't it idle crappy if the timing was that far off? And it is all stock (its not OHC, its pushrod)

Is the boyer ignition good? Also is the zener diode regulating the voltage correctly?

>As far as i am aware yes to both. it has good spark and the battery is charging correctly.

>Could it be a fouled plug making it run that bad? i havnt put a new spark plug in it for a while, and i was having issues with it fouling plugs before i started having this problem.

Check the voltage coming off the regulated side when you get it reved up. If its over charging, it could be messing with the ignition.

If youve got a timning light, Id watch the timing when you get it revved up too, see if it moves at all. And it could run nice at idle if the timing was off when you get the speed set with the screw, but the slide could be way higher than it should be if its retarded. If there was a way to lock the timing down at say 30 degrees or so BTDC id see how it ran like that. (basically fully advanced all the time). Because if its idling ok at say 12 btdc but wont advance, it wont want to rev at all. Or possibly the "dwell time" isnt correct in the ignition and the spark is going to hell when it revs up...

ok ill check that

thanks

Or possibly the "dwell time" isnt correct in the ignition and the spark is going to hell when it revs up...

That sounds likely, because the symptoms he describes are the same as dirty or misadjusted points, but he doesn't have points.

I don't know if this will help any, but here's the set up pages for the boyer brandsden ignitions.

BoyerBransden05.jpg

BoyerBransden06.jpg

Another thing to try would be to put the points and condensor back in just for test purposes and see how it runs.Since your victor is stock swapping carbs around is the wrong way to diagnose this problem.If it was jetted for the stock set up there should have been no problem at the carb but I would still check the carb there are about three different needles and recievers for an amal concentric carb.It should come with stock a 930 or 30mm carb,main jet 230,pilot jet 25,needle jet 107,slide #3,with the needle in the middle or #2 position the needle I believe it's supposed to have 2 small rings at the top above the clip grooves,the jet holder in the carb could be one of three different ones and I'm sure you need the one that has a short shoulder at the mainjet side.You have to have the right one or it throws the jetting way off.Make sure this so before you start tuning or you will be chasing your tail.Make sure your battery is holding a 12 to 12.5 volt charge static and 13.5 to 14.8 with the engine running.If not change the battery it's probably going bad and solid state likes to have it's voltage I've personally seen boyers shut off at 9 volts or less.Check valve adjustments and also for vacumm leaks around the intake.I have a 441 all stock with points and a mightymax that I have been racing for about 5 years and it runs like a dream.

ill check the battery too, its a oldish battery so maybe its just no good any more...

Atleast with a battery, you won't need to worry about high voltage as much.

Without the battery, and using the zener diode alone for voltage regulation, I had a boyer get torched. Which brought on erratic timing.

CYA JOE

Obviously check your ignition system again and maybe put the points back on to try. I'm just wondering though, as Beezerjoe said, the correct carb should be a 30mm bore. If the bore is too large, the signal will be weak from the engine and it won't pull any fuel. Try a smaller carb, you'll have a much greater lowdown and midrange because it will work efficiently. Imagine trying to suck a glass of water with a thin straw and then a 16mm hose. It takes a lot of effort to get the water to move with the larger bore (and it's slow). This could be happening with your carburettor. Large carbs aren't always the correct answer.

I had a Spitfire cam in my A10. I then fitted a 32mm carb thinking it was going to be even more powerful. It was awful, no lowdown and, because they don't rev high, there was no benefit at the top end either. I put the 30mm on it and it was greatly improved. I may even try a 28mm yet.

Anyway, good luck and I hope you get it sorted.

Just wanted to check and see if you made any progress on that victor.

Not sure what your problem is.. but that is one really nice bike! Hope you get it running good.

so far ive bee pretty busy and havnt had time to really look at it. thanks YZ, i really put a lot of work in it and would hate to not be able to get it running.

unfortunatly, i dont think i have the points still, they were not in very good shape when i started working on the bike and didnt think i would have to use them : /

I had another thought about your problem and I don't know if it's appllicable in this situation I have been told that the boyer needs to have an ignition coil with the correct resistance but I can't remember what the value is or which terminals to check it from on the coil.Maybe YZ400FJOE has this info at hand.I can get this info from a fellow brit bike mechanic friend of mine who has installed several boyers.I would also like to ask if you overhauled the engine is there a possibility that the cam timing could be off?Also which stator do you have in that unit is it a 2,3 or 4 wire?The 2 and 3 wire stator were for a battery ignition and the 4 wire is for a magneto.If this had a mag on it then there is a chance the coil is wrong but with out being there to see it I'm only guessing.Another thing you might try is make sure the engine is properly grounded to the frame when I first got mine going all the parts were good but no spark until I ran a ground wire from the frame to the engine.It was insulated by paint and not allowing the plug to to jump a spark to ground.Hope this gives you some more to go on.

i think its 2 wire, it could be 3 but im sure its not 4

A 1969 BSA most likely is a 2 wire since the 3 wire alternators are in earlier 60's models.That is the correct stator for a battery ignition so the coil should be the right one.The magneto or energy transfer ignition used a coil that was clipped into a C shaped lamenated steel mount and then bolted to the frame.What bike did you rob the suspension from?I've got a couple old 250 BSA frames laying around and was considering building one similar to yours.

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