2002 GTX (carb) Rave Question

[lschif]

I have a 2002 GTX that is only getting to about 6k rpms. Riding last weekend, it would do the normal almost 7k - a few family members rode throughout the day and now it is lagging. I found the crankcase line (connected to the check valve) unhooked. I hooked it back up to no avail. Since then, I've: 1) rebuilt the raves; 2) blown out all the lines going to and from the solenoid; 3) tested the inlet to the solenoid by unhooking the inlet line and placing it in a cup of water - got some bubbles at high rpm - nothing magical though - don't really know what to expect; 4) tested the solenoid outlet to the raves by unhooking, running a line into a cup - again, got a couple bubbles at high rpm; 5) put 12 volts across the solenoid - it actuated; 6) ran her in the water with the supply line to the raves disconnected - absolutely the same performance as when the line is connected.

My questions: 1) how much air should be coming out of the crankcase line to the solenoid input? 2) How do you test the solenoid electrical input from the MPEM / is there a fuse / etc? 3) could a faulty check valve be limiting air to the solenoid? What am I missing - thanks.

 

[SabrToothSqrl]

#1 compression test.
#2 all other tests.

if you don't have valid compression numbers, you don't have a working engine.

also, have you thrown new plugs at it? always new plugs! for $4 it's always worth new plugs.

 

[lschif]

Yes, I put new plugs in it.

I've never checked compression on it - anything special I should know? I saw that the DIs had an odd procedure, but I'm thinking that since this is the carb version, it should be pretty straightforward.

I'll have to wait until Friday to get back to the lake - thanks very much.

 

[- BiRkS_]

I like to close the fuel selector, plugs on grounding posts, WOT, 3 times per cylinder, take the middle reading for each cylinder. 951 should be about 135 psi anything less than 120, it won't run very well at all.

A simple test for the raves is to pull off the caps and take the springs out. That basically will open the raves with the little exhaust pressure. You may notice a lumpy idle and crappy low speed, but high range you should get 6800+ rpm Its possible your check valve is clogged in the pulse line from the crankcase, You can simply bypass it (that would explain why the line blew off in the first place.)

Then read your plugs. If you are running lean, you may be roasting your top end, and thats why your rpm's have dropped. But with a two stroke you can feel it running lean. from 3/4 throttle to full throttle, you should feel smooth acceleration, not a bog or wahh sound with little or no higher rpm. Let us know what you find.

 

[lschif]

I very much appreciate the help - Finally got back to the lake - compression for the front cylinder was 120, rear was 130. For grins, I threw a new check valve and solenoid on - no change. It will accelerate well to about 6000 rpms - from 3/4 throttle to full throttle there is no change.

I pulled the springs from the raves and no change - 6000 rpms.

I haven't looked at the new plugs yet, but the old plugs were relatively black - wouldn't I expect tan/white if I was running lean?

I hadn't mentioned it before (but I've read about damage reed valves), we did get water in the engine last Labor Day - I pulled the plugs, got it running immediately and we ran the devil out of it all last fall, winter and spring up around 7k RPM - until I noticed the RPM issue last weekend.

Anyway, thanks for the help.

 

[SabrToothSqrl]

Depends how old they are. (Plugs).

What oil do you run? How many hours on it?

Fuel filter clean?

The 120 isn't as bad as the 120 vs. 130.
That variance can indicate a problem.

Is the throttle opening the carbs all the way?

You can remove the huge intake and grab a makeup mirror.

Did you check the TPS sensor along the throttle cable?

Shows 5v 0-80% and 81%+ shows 0v I think. Purple to black.

Bad fuel?

How's the jet pump?