36mm vs. 36.5mm carb & PVL

[Mike Hufnagel]

I have 2 36mm mikuni carbs, One is stock 36mm & thye other has been bored out to 36.5mm (came off a road racer & has a different slide. It's going on a 250 scrambler motor that has reeds & a pvl. Which one would be more preferable regardless of the slide?

Also, I was told that a pvl ignition produces a weaker spark and that it takes a different plug than normal. Is this true? The plug I'm using now (without looking at the numbers) also fits a PW50

[tomale]

HI Mike, I put a bored out 34 on my MC 5 motor, but it is the same motor as the scrambler motor... the reason I did that was because I had trouble getting the 36 to fit right... angle of the intake was not right.. It might be different with the reed valve, maybe some of the other guys can speak to that, I have done very little to my 250 motor and it screams... once I got the mikuni sorted out... I ride it in the plus 50 class and some of my competitors thought it was an open class bike... I found that between the Protopipe pipe and the Mikuni carb it pulled so much better than the Bing.. It already rev's like an 125 on steriods I can't imagine what it would be like to put a PVL on it, and yes by the way you do have to use a different plug, follow the instruction for the PVL to the letter...
Also make sure, do not just assume that the grounding from the motor to the frame is good, If you have to, take the motor out and reclean the area that will be used to ground the motor to the frame, this too is very important for the PVL. If it were me, I would have Penton imports rebuild my Motoplat. All of the bikes that I have with Motoplat's are still running good, but then I am very careful to keep the grounding clean. Good luck and let us know how it goes.

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)74'
250 hare scrambler (project bike)

[TGTech]

The PVL ignitions have a strong spark. The Motoplat KV is about 26,000 compared to the PVL at 32,000.

The only issue is the grounding between the spark plug and the coil/CDI. If there is not a good grounding, the stator can die over time.

Dane

[tomale]

I recently picked up a bike that had one owner, It looked like it had been ridden a few times and then put away for a very long time... I took the tank off and started my clean up mode.. To my surprise, the Coil looked like someone had taken it off and added small pieces of rubber to Isolate the coil from the frame,, They did not do a very good job and I am sure that it had run that way but I quess they really did not understand what Dave was talking about either.... Can't wait to get it back together to see if it does have spark... (I would have tried before but as it turned out, the piston was stuck and I could not turn it over,,, It will need a new ring and a gasket...

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)74'
250 hare scrambler (project bike)

[SouthRider]

Some early dirt bikes came with the coil hanging on a piece of hard rubber - with a separate ground strap going to the frame. They worked fine this way - but the extra chafing probably caused as much or more damage as the vibration from a fixed mount.