2104 Grom.. 2t conversion

[Czakky]

Frustrating when you don't know for sure what happened.

[m in sc]

took head off, piston dome is perfect, only got hot at exhaust side, and quick. (the face). im thinking late timing, ive never seena motor go this quickly though. going to need a bore and piston though, the cyl is smeared around the exhaust port. IMHO, the only 2 thing son this motor it could be is timing, or a blocked exhaust, which im 99.99 percent sure it cant be since i took the whole pipe apart and rewelded it.  (but ive seen this with a broken baffle on a chamber before). sigh. 

[Evans Ward]

I hate that for you Mark but feel strongly you'll get it sorted.

[Kawtriplefreak]

Damn

[85RZwade]

Any chance of saving your cylinder bore with muriatic acid? I've only tried it once, but it worked for me.
Wade

[m in sc]

maybe, but i also have a spare cylinder, im not worried about it. I can get it rebored, either of them and a new piston for around 200 total.

[m in sc]

so in digging in deeper on thought about this, Im pretty sure i have the wrong rotor for the motor. i bought it off ebay, might have been off a different year or model (maybe lt500)  reason being is, the trigger and pickup are fixed. the book states that timing at 6k should be 12 degrees. physically, there's NO WAY this can fire that advanced, the trigger is at 6 degrees, maybe, firing static, max advance. Im not sure it its from an RM or 500 or what, but im going to move it (the stator plate) around while im waiting for the spare cyl to get done and program the offset with the zeel and get a more advanced baseline in it. ( the zeel gives a max of 50 degrees)

if you are familiar with a programmable cdi, you need the physical pickup to be at least at max advance position, physically, for it to work right. a curve is nothing more than a programmed delay in an ignition box. 

[m in sc]

as an update, i sent the spare cyl off (which was actually on the stock bore when i measured it) to be checked, probably bored 1 over and a new piston for it installed.

so, i still have the old one on the motor and am able to turn the motor over and check timing with a light. i re-positioned the stator plate  which involved making new mounting holes in the plate, so there is now a static angle of 18", then i used the zeel programmer to address this, it now allows for a curve that goes beyond 6 degrees BTDC, my initial curve is now

500 = 6 degrees
1200 = 6 degrees (manual spec 6 @ 1000)
2500 = 9 degrees
6000 = 12 degrees (manual spec )
9000 = 10 degrees
12000 = 7 degrees

rev limiter set to 10k.

this should be a good start. I am able to spin the motor up to 1000 rpm with a fixture tool i made to spin the crank over at the flywheel with a drill, so i verified with a  timing light. I still for the life of me figure out how this was supposed to achieve 12 degrees when the rotor/trigger was fixed. However, i suspect the rotor was the culprit since i had to bu one of those, and i'm guessing it may not have actually been for that model, and the trigger was in the wrong place. No way to verify that though. 

[Kawtriplefreak]

Shit happens YO. You will get it...

[m in sc]

oh i know. just sharing what i found. some insight to dealing with the zeel mostly.

[Kawtriplefreak]

Cool.

[50gary]

That pipe looks like it's machine welded?  Outstanding work.
  Cheers, 50gary

[m in sc]

thanks, its appreciated. Piston should arrive this week. want to get this thing going again. In the meantime been working on some long overdue car stuff. 

[85RZwade]

Getting late in the day on your side of the continent; any luck with the Grom, or are you still under a car?
Wade

[m in sc]

funny you mention that. I got it back together today, but its raining.  This was about an hour and a half? or so ago. test ride tomorrow but it sounds WAY better. timing sitting at 12 degrees at 6k, at 8 at idle.

THIS is what VERY  late ignition timing did to the last one. I had to move the plate 17 degrees  to get it to fire at 8 degrees at idle and 12 at 6k. so, im assuming the rotor i bought was 'off' as everything else was original to the motor. (i didnt have the rotor so i ebayed one and burned myself not verifying)



new and fresh this morning: