Still Having A Cylinder Drop Out At Top RPM

SRX_700

SRX_700

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Joined
Jan 14, 2011
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807
Age
55
Location
Toronto
Revs up to 8,500 then falls back to 7,500 with a wide open bog sound. PTO plug looks fouled and dark. If it is below 32F, I don't notice the problem as much. Runs all day at 8,000 RPM but if I punch it wide open, it falls flat on its face. I was riding at 34 F today and did it more as the day went on. Everything stock with 2001 jetting (150, 148.8, 148.8). Compression when motor is warm is 115, 115, and PTO is at 110. New coil and plug cap for PTO cylinder. New clutches with stock setup. Not sure what the problem is, could it be?

1) Reeds (starts 5 pulls cold)
2) Incorrect jetting (2001 stock jetting too rich with the temps)
3) Lower compression (gauge might be inaccurate but PTO is lower then other 2)
4) Wire rub thru
5) Stator

I have been chasing this issue for 3 years now. All electrical components work great, grip warmers, hi/low beam etc. Plug pics below. First pic is PTO plug last night riding with no WOT bog (temp below 32 F). Second is PTO plug from today when it was 34 F. Plug seems to foul and then won't fire correctly at 8,500 RPMS.
 

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Yup. Today. And when it gets colder out, it looks like the one on the left. If I was to take the motor apart, what should I look for?
 
SRX_700 said:
Any other suggestions besides ripping apart the motor?
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are u sure all pv still hook on cable .....did u try a new belts..my sled did that till I blow a rod bearing :o|
 
I checked PV and it seemed fine. Would a PV that does not open cause a plug to look like that? I have a belt with 600 miles on it. I have not tried to put a new one yet. Not sure that would really cause a plug to foul at top speed, however. What cause your rod bearing to fail?
 
. ...it did pull good for 2 or 3 wot and then rpm did start to fall...till a day it caboom ...I think moisture was the cause of it ...the pto main was not in very good shape ....kind of rust ...did u remove your reed to check them ....I dn't think a pv would make the plug the change that way
 
I am going back up on Monday as the sled is 2 hours away from me. Will check the main jet in the bowl as well as the reeds. Somewhat ruling out electrical as it is only affecting one cyclinder on a consistant basis.
 
you could look at crank seal and bearing nothing else in there ......maybe you could remove only that cylinder ...
 
YAMMIEGOD3:16 said:
THAT PLUG SHOWS ENGINE DAMAGE . THATS SILVER ON THAT PLUG AIN,T GOOD. 3:16 (yammie tony)
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is it silver tony or its a flash effect .........
 
Wow Tony. No silver whatsoever. It's black and wet with carbon. Mod is right about the flash effect. Compression is 110 and the others are 115. Plug is fouling over time and cutting out at high RPM. When it's colder, it seems to burn cleaner and the WOT bog is less apparent.

Mod it is a 2000 SRX. Have not check the flywheel for rust.
 
modsrx said:
is it silver tony or its a flash effect .........
Click to expand...
Looked like a flash effect to me....

My 01 had a similar issue, bought a used stator and ended up using my original magneto with the pickup coil I got with the used stator....Pickup coil was my culprit, but checked out in the bench tests.... Just food for thought
 
Yeah. Looks like I will continue to swap parts out until it is right. Just odd that it does not happen when it is below freezing and plug colour goes back to normal. Will start with putting a smaller jet into PTO carb and see if that makes a difference.
 
SRX_700 said:
Yeah. Looks like I will continue to swap parts out until it is right. Just odd that it does not happen when it is below freezing and plug colour goes back to normal. Will start with putting a smaller jet into PTO carb and see if that makes a difference.
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u will seize if u do that .....did u remove your reeds ...do u run stock air box ?did u check the needle and seat...maybe something stock in the air bleed carb....not sure its ignition if its run better went its cold ...maybe wrong jet ???sometime they are hard to read
 
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Have not looked at the reeds yet. Will do that Monday. Carb has been apart last month at the beginning of riding season. Mains looked good. Did not check Needle and Seat and top hat filter but I did last year. Like I said it will pull 8,000 rpms all day above freezing, when I pin it, it falls flat down to 7,500. Happens when the clutches have fully shifted out. Everything is stock.
 
let uss know Monday and make sure u didn't put a wrong jet into that cylinder ..you could swap to another carb
 
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