Idle problems with BigBore 750 rephased

[chizler62]

Is it hard to start or just run poorly at idle? All throttle range?

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[Hazer]

it is hard to start - sometimes i kick at least 10 times, then wait, suddenly it would start. then idle runs really poor but when i go faster the bike runs ok ... at least on the right zylinder.

 

[chizler62]

That's sounds as tho you're charging up the CDI. No battery? The powerdynamo is a great ignition. I went with a heavy flywheel to ensure for a easier batteryless start.
1k is standard?
Do you know what size you have?

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[Hazer]

i am running a 26 oz (750 gramms) rotor that comes with the only system by powerdynamo suitable for a 277° rephased engine.

and i run a battery but it is only for the lights. but i might try the earlier mentioned converter to add the battery power to the ignition. would make sense right?

 

[TwoManyXS1Bs]

You might try to double-check your wiring layout, avoid adjacent runs, per this caution:


The 'reduced gap' spark plug test could confirm the need for more power at kickstart speeds...

 

[chizler62]

26oz is almost half what it should be IMO. I wonder if they did that in order to fit both pick ups off the crank? Is it a internal flywheel or does it look like a banshee? Did you have to remove any of the case to install the second pick up?

I'd get some sticky wheel weights and put 20 oz on the flywheel and see if it starts better and runs smoother without stalling. The heavier flywheel keeps that moment of inertia and will help starting, idle and acceleration. It'll smooth out any snappiness and get the power down a bit better.

Again. I have a, I think, 46 or 50 oz flywheel with my 750 at 11 to 1 and it starts good with expected effort by kick!

 

[vsop-dk]

Hazer any news about the Heiden and Powerdynamo issues? Hope you have it sorted, just wanted to hear if there were a solution.

 

[Hazer]

sorry for getting back so late: we recieved the engine, built it back in the frame ... and it works fine since then ! we changed nothing on the cables / electrics and heidentuning told me, they also changed nothing. it's a miracle haha. the one thing i realized is, that it starts better without pulling the choke out. apart from that there are still some rare stutters in idle when i am waiting at a redlight. but all in all the engine now feels like a real big bore, the power is insane. so far i pushed once to over 175 kmh and there was still enough power to go faster.

 

[vsop-dk]

I'm happy to hear it's solved. Guess something along the way got fixed.

What's your experience with Heiden and engines?

Could you pm me with some details with purchase and price etc! Would appreciate that.

 

[Hazer]

This has been a while and I want to give an update. After sending in my engine to Heidentuning and getting it back with a "all good" reply and a few days of running "ok" and after that another summer wasted on a engine that won't run properly (and never has), I discovered XS-Laden in Bavaria and sent my bike there in autumn 2017. When they opened up the engine, they discovered a total mess. The basic problem are the way to thin cylinder sleeves of the 750ccm bigbore kit. A solid 750ccm is not possible without modifications on the case. 6 months later I finally got a really powerful engine with custom cylinder sleeves and totally rebuild engine from XS-Laden and the engine is finally running how it was supposed to from the start. Boy what a difference! Since then I put around 3.000 km on it, no problems at all. So in the end I wasted thousands of euros when trying to find out, why the engine was never running properly (Exchanging carbs, exhaust system, etc.). I can't speak for other people out there who bought their 750 bigbore from Heidentuning, but getting a "all good, no problems" reply AFTER sending an obviously destroyed engine back to the builder is really beyond my understanding. I also attached some pictures of XS-Laden, when they opened up the engine.