Hi. I switched to a bigbore kit 750 rephased with a Powerdynamo ignition system, all done by Heidentuning in Holland. Since then, I have the problem, that the engine runs poor in idle (right zylinder runs good, left zylinder runs bad) and it backfires with smoke from the right carb (open airfilters on brand new Keihin carburators). We even went to Powerdynamo here in Berlin, they couldn't tell us why it runs so bad. So in the end I sent the whole engine back to Heidentuning - they found nothing wrong with the engine itself and tested it together with my carbs - all fine they say. So i am running out of ideas here ... Engine is fine, carbs are new, so maybe the ignition coils seem to be bad. What I heard is, since I run a rephased engine, I now have the powerdynamo set with two ignition coils and those are together placed under the tank – and if you place them too close together there can be problems with the ignition. Does anyone here in the community have similar problems with a rephased engine and bigbore750 and the powerdynamo system? Any help is welcome !
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Idle problems with BigBore 750 rephased
- Thread starter Hazer
- Start date
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- Tags
- carburetors custom engine
I have no experience with the Power Dynamo system, So I can't say much about that.
Most often when one cylinder runs ok and the other no. It is carb related.
I might suggest checking the carbs for dirt in the idle circuits.
Are these Keihin carbs those Mike's XS was selling? Some of them are not good carbs.
"open air filters", are these cheap K&N knock offs or good filters, Long straight foam filters. The K&N type short tapered filters cause tuning issues with vacuum carbs. The longer straighter versions are better but still not ideal.
Leo
Most often when one cylinder runs ok and the other no. It is carb related.
I might suggest checking the carbs for dirt in the idle circuits.
Are these Keihin carbs those Mike's XS was selling? Some of them are not good carbs.
"open air filters", are these cheap K&N knock offs or good filters, Long straight foam filters. The K&N type short tapered filters cause tuning issues with vacuum carbs. The longer straighter versions are better but still not ideal.
Leo
Thanks for your suggestions. I've got the longer straight original K&N filters for more air intake since the updrade. The Carbs are brand new, directly ordered here in Germany ( I am located in Berlin ) and have run less than 200 km so far. The only thing that was not changed for new parts since the 750 upgrade are the intake sockets so i will change those when i get back the engine from holland. what is strange is, that the left zylinder runs poor but the right airfilter starts to pump smoke when backfiring.
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650performance
XS650 Addict
Since the engine and carb setup runs OK in Holland (assuming you believe Heiden's account) out of the bike, but runs poorly in the bike, that suggests to me that you probably should double check all the electrics, especially anything around the ignition system and grounding points to the frame. As an afterthought, the throttle linkage would also be different from what Heiden used. No kinks in a cable, etc.?
throttle is fine. but yes, I guess I have to rebuild all cables from scratch. again. I mean the cable tree is all brand new but I am pretty sure that the problem is hidden there. The guys from powerdynamo will run tests with all parts so I can be sure that there is no failure hidden there – although they say they are sure it is not their system or their parts, they just think that a heavy modification like a bigbore kit might not work properly in the end. but i don't think so.
650performance
XS650 Addict
It's a small thing, but just to make sure the ignition resistance is a low as possible, I recommend you buy a set of Denso Iridium spark plugs. Don't touch the gap; it will be OK as it is and can be easily damaged.
I'm assuming the correct heat range is 24 or 25 (depending upon your compression ratio), but you can find a cross-reference table on the internet to ensure it's the same heat range as Heiden recommends.
I'm assuming the correct heat range is 24 or 25 (depending upon your compression ratio), but you can find a cross-reference table on the internet to ensure it's the same heat range as Heiden recommends.
tonyc
XS650 Guru
If your electronics checked out along with your engine, it could be your exhaust system or wiring.
Posted via Mobile
Posted via Mobile
Since you have two ignition coils, you can swap the plug leads and spark plugs over. If the problem transfers to the other cylinder you have an ignition problem. If it remains on the same cylinder it is something else. It looks like you have Mikuni TM 34 carbs as well from your photo.
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Oh man of course those are Mikuni carbs, sorry for mixing this up. How did I come up with Keihin? It was late 
Yes, we switched the spark plugs once - same problem. Funny thing is that everyone "involved" in the bike says it is another problem but not from his side: Heidentuning says the engine is fine and there has to be something wrong with the parts from Powerdynamo. Powerdynamo says, it is the heavy modification that comes with the Bigbore which has poor performance (which I doubt - if you execute it all properly it is a reliable system and upgrade I guess, why else would so many people do it). And my mechanic, who helps me with all that stuff coming together, says it is the Powerdynamo system which is super difficult to adjust AND the engine ....
Yes, we switched the spark plugs once - same problem. Funny thing is that everyone "involved" in the bike says it is another problem but not from his side: Heidentuning says the engine is fine and there has to be something wrong with the parts from Powerdynamo. Powerdynamo says, it is the heavy modification that comes with the Bigbore which has poor performance (which I doubt - if you execute it all properly it is a reliable system and upgrade I guess, why else would so many people do it). And my mechanic, who helps me with all that stuff coming together, says it is the Powerdynamo system which is super difficult to adjust AND the engine ....
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My first suggestion was not helpful at all. I missed the point that you had rephased the motor my apology’s.
Back firing........................indicates ignition timing problems..................have you used a timing light to look at the actual spark timing?
Is the spark advance, mechanical or electronic and does it work; i.e. can you see the spark advance move with your timing light?
Have both carbs been tuned.................float levels correct, mixture screws adjusted properly, etc.?
Is the spark advance, mechanical or electronic and does it work; i.e. can you see the spark advance move with your timing light?
Have both carbs been tuned.................float levels correct, mixture screws adjusted properly, etc.?
we sent the engine back to holland to have it checked again by heidentuning - all fine.
so i got the spark exhaust now and we will rewire everything next week.
does anyone here use the PAMCO rephased 277° version with a bigbore? the system costs only half of the price that the powerdynamo system costs - well almost. so maybe i should get that PAMCO system? seems to be the system of choice in the states ...
so i got the spark exhaust now and we will rewire everything next week.
does anyone here use the PAMCO rephased 277° version with a bigbore? the system costs only half of the price that the powerdynamo system costs - well almost. so maybe i should get that PAMCO system? seems to be the system of choice in the states ...
If everyone throws their hands in the air and blames some one else , and your wiring is spot on get a Pamco kit . It would also be good to borrow a "good" set of BS38's and give them a go. Good luck with your project. tim
chizler62
XS650 Addict
The pamco isn't near the quality of the Powerdynamo.
What compression ratio?
What grade fuel?
What's your flywheel weight?
I'd suspect, as I have a dynamo and a 750 not rephrased, it'd be something silly.
Posted via Mobile
What compression ratio?
What grade fuel?
What's your flywheel weight?
I'd suspect, as I have a dynamo and a 750 not rephrased, it'd be something silly.
Posted via Mobile
chizler62
XS650 Addict
Do you have a 50mms/2" dial indicator?
does it run bad throughout entire RPM range?
I'm not a fan of rephasing the crank. Neither is powerdynamo for what I've been told.
What's the gap of the pick up?
Posted via Mobile
does it run bad throughout entire RPM range?
I'm not a fan of rephasing the crank. Neither is powerdynamo for what I've been told.
What's the gap of the pick up?
Posted via Mobile
The PowerDynamo ignition system is a magneto type ignition system.
Magneto ignition systems without impulse coupling have low ignition energy at low rpms.
A simple test for weak ignition energy:
Reduce spark plug gap to about 0.015" (0.40mm)
Start engine. Note any changes to starting effort and idle smoothness.
If engine runs better, suspect weak ignition.
The Pamco System (with a battery) will provide hot/high ignition energy at idle speeds.
The Pamco E-Advance System includes a special retard-start timing feature.
Bitte, gluck haben...
Magneto ignition systems without impulse coupling have low ignition energy at low rpms.
A simple test for weak ignition energy:
Reduce spark plug gap to about 0.015" (0.40mm)
Start engine. Note any changes to starting effort and idle smoothness.
If engine runs better, suspect weak ignition.
The Pamco System (with a battery) will provide hot/high ignition energy at idle speeds.
The Pamco E-Advance System includes a special retard-start timing feature.
Bitte, gluck haben...
chizler62
XS650 Addict
