WTF did I do?

4185 Views 53 Replies 16 Participants Last post by GarDog, Feb 25, 2010

Overspray

Discussion Starter · Feb 15, 2010 (Edited)

WTF did I do? I can't believe I'm asking for "your" opinions, but let's hear them.

On New years, I put too much NOS to the 730. (miscalculation on my part) Got a little flash and some white smoke up through the carbs.

Now it starts and runs, but is way underpowered and stumlbes under hard load. Especially if you get out of it and right back into it. It doesn't die, just runs like a 1500 rpm rev limiter or something. It gets worse as it warms up.

I replaced plugs, CDI, jetted back to a previously good running setup.

If it didn't fluctuate or was hard starting, I would think it was rings or valvetrain. No smoke or noise though. I need to pull the carbs and see if I ruptured the vacuum diaphram. When it doesn't stumble, it runs fine other than being short on power. I figured the crossover tube could make it run on one carb.

Other than that, I got nothing.

Okay, lets hear from the brain trust.

1 - 20 of 54 Posts

fastfatboy

· #2 · Feb 15, 2010

Sounds like ya got a handle on what to look at. Hope the rings and or cylinders aren't hurt.

Overspray

Discussion Starter · #3 · Feb 15, 2010

fastfatboy said:
Sounds like ya got a handle on what to look at. Hope the rings and or cylinders aren't hurt.

From your mouth to Gods ears brotha.

It's the only thing that accounts for the itermittency. I was hoping that someone has heard of this sort of thing or had any other ideas.

Smithy1999

· #4 · Feb 15, 2010

Sounds to me like you broke a piston land. Starts fine runs fine but when you get that engine going the exhaust gases blow past that land causeing a loss of power under heavy load.

GarDog

· #5 · Feb 15, 2010

piston land...i'm not saying it's impossible...but I usually see hard starting as a symptom of that....
I'm gonna go with badhear on the diaphram on this one....

rocket joe

· #6 · Feb 15, 2010

GarDog said:
piston land...i'm not saying it's impossible...but I usually see hard starting as a symptom of that....
I'm gonna go with badhear on the diaphram on this one....

I agree with FatDog! :lol:

bubbasoffroad2

· #7 · Feb 15, 2010

If you want to try my 38's just let me know they will need cleaned up still have sand on them

VFORCEJOHN

· #8 · Feb 15, 2010

popped a diaghpram out of the seat under the plastic cap.

pull the filter and see if they are opening all the way.

if it doesn't seat right you hold no vacuum in the starting circuit of the carbs (that's how the chokes get their vacuum from

John

NovaKaw650

· #9 · Feb 15, 2010

VFORCEJOHN said:
popped a diaghpram out of the seat under the plastic cap.

pull the filter and see if they are opening all the way.

if it doesn't seat right you hold no vacuum in the starting circuit of the carbs (that's how the chokes get their vacuum from

John

Possibly what he said, also make sure that a carb didn't blow up out of it's manifold.

Overspray

Discussion Starter · #10 · Feb 16, 2010 (Edited)

NovaKaw650 said:
VFORCEJOHN said:

popped a diaghpram out of the seat under the plastic cap.

pull the filter and see if they are opening all the way.

if it doesn't seat right you hold no vacuum in the starting circuit of the carbs (that's how the chokes get their vacuum from

John

Click to expand...

Possibly what he said, also make sure that a carb didn't blow up out of it's manifold.

I checked the mani's right away.

Thanks for the input.

Overspray

Discussion Starter · #11 · Feb 20, 2010

The carbs seemed fine, although I guess that diaphram could've slipped back into place when I looseend the clamp. The slides seem to move well when revved now. Like a dumba$$ I didn't check it until after I pulled it apart.

I did a makeshift leakdown test and couldn't hear anything blowing buy.

I am quickly running out of ideas.

Any theories welcome.

NovaKaw650

· #12 · Feb 21, 2010

Check the ignition timing. Maybe it spun the flywheel when it backfired.

Overspray

Discussion Starter · #13 · Feb 21, 2010

Can i do that with a regular timing light?

NovaKaw650

· #14 · Feb 21, 2010

badhear said:
Can i do that with a regular timing light?

I've done it with a timing light, but it's been years since I did it.
I do think it was straight-forward; hook the pickup to the #1 cylinder (front one, most likely, check the manual), 12v power source, pull the viewing plug and check the timing. I think I covered the hole with a rag and pulled it away when I had the light ready to go because the oil will fly out with the engine running. Wear your safety glasses. If you have a degree key, it will throw the timing mark off a bit.
Hopefully someone that's done it recently will chime in. I think VFJ has checked them with a light.

Overspray

Discussion Starter · #15 · Feb 21, 2010

I'm assuming there are other ways as well?

NovaKaw650

· #16 · Feb 21, 2010

badhear said:
I'm assuming there are other ways as well?

Make sure the piston is at TDC and see if the mark on the flywheel is lined up with the mark in the viewing hole.

700ccMARSHMELLOW

· #17 · Feb 21, 2010

I had a warrior that acted like that. It wound up being a small split in the manifold. I never found it till I took the thing apart. Put it back together with a new manifold and it ran like it should

Overspray

Discussion Starter · #18 · Feb 21, 2010

Interesting thought, I wonder how hard it would be to hurt those UPPs?

Overspray

Discussion Starter · #19 · Feb 21, 2010

Has anyone ever broke the key on one of these things?

BS750

· #20 · Feb 21, 2010

Yes it is possibly, and I have seen sheered flywheel keys.

1 - 20 of 54 Posts

This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.