96 gtx odd problem! And 96 gti problem

[ape1972]

Hello Everyone,
I bought a 96 GTX last year and have not been able to get it to run right. When I ran it this weekend I thought the problem was solved but nope! When I first ran it, it ran really good with no hesitation or bog but as time went on (ten minutes or so) at full throttle i could feel it wanting to bog down so I would back off the throttle. It got to a point where I couldn't even start it. When I would try to start it I got some back firing.

This is what I have done to the GTX so far: Replaced all gray tempo lines, cleaned out carbs by hand and ultra sonic machine, cleaned fuel selector switch, replaced spark plugs, new battery, new rectifier, new wear ring.

I'm really at a loss... I had a 92 GTX and a 94 and they never gave me this much grief.


NOW FOR THE 96 GTI!

This ski ran much better then the GTX. The problem I have with it is that it would totally bog down at random times to idle. I would have to feather the throttle to get it back to speed and it would be fine for a little while then do it again. One thing that I noticed when I checked the engine is that it seem pretty hot. I couldn't keep my hand on it without burning it. It didn't seem normal. Also when I when there is two or more people on it it struggles.

Thank you all in advance for your help,
Adrian

 

[Bills86e]

Too much Air, .........not Enough fuel. (or no lubrication) Check all. [ RV oil line(s) ] gti & gtx

raves on gtx may be stuck

 

[ape1972]

Thank you for your reply! I will check it out this week and let you know the results.

Adrian

 

[ape1972]

Okay so here's an update!
I took the rave valves off and cleaned them really good. I know carbon builds over time but I don't think this looks normal. I'll include before and after pics. After I put everything back (exactly how it was) I tried starting it up and it backfired so loud it scared the crap out of me. What could cause it to run great then no run at all? Makes no sense!

 

[mikidymac]

The raves look normal but dirty.

A backfire it typically from leaking needle and seats and fuel fumes in the exhaust.
Really the only other less likely cause is a sheared flywheel key or rotary valve out of time.

 

[ape1972]

Needle and seat is new... Just doesn't make sense that it ran great for ten minutes or so. Bogged down at WOT then won't start with backfiring.

 

[mikidymac]

I would double check the carbs.

I had one do the same thing and it turned out there was a tiny nylon thread holding the needle open like a tooth brush bristle that I have no clue where it came from.

 

[ape1972]

Ok Everybody,
I took the winter off and now i'm back at it trying to figure out this backfiring problem.
Here's what I have done thus far...
1. I pulled the carbs and both are very clean with no issues at all!
2. I checked the rotary valve for timing and also checked for a bad brass gear and all is good!

I'm going to pull off the Stator cover and check for a sheared key.
My question is that if it's not a sheared key or any of the issues that I have listed, what else could it be???

Thank you in advance for your help

 

[Chester]

When you have the flywheel cover off, inspect the pickup coil to see if the mounting plate broke.

Chester

 

[ape1972]

Thanks Chester,
I will check that for sure! Just out of curiosity could it be the MPEM? I replaced the rectifier with an aftermarket one. Could that be bad even though its new?

Thanks again

 

[ape1972]

Ok so here's where I'm at now...
Checked carbs.
Checked rotary valve and brass gear.
Pick up coil mounting plate is okay.
I am curious about the flywheel key though but I took pics of it to get all of your expertise.
Does the key look sheared?
Thanks again for the help!

 

[mikidymac]

Can't tell from the pictures.

 

[ape1972]

Okay, I will pull it off

 

[ape1972]

Sorry for the major delay everyone!

So I pulled the flywheel off and the key is perfect. Please view the attached photos. What else could this possibly be?

Thank you all so much for your help.

 

[ape1972]

So here is everything that I have checked to date! This 96 GTX has a major backfire issue.

Checked carbs.
Checked rotary valve and brass gear.
Pick up coil mounting plate is okay.
Checked the flywheel/drive shaft Key (good).

I'm not sure what to check for next... Please advise

 

[ace422]

In your original post you said you cleaned the fuel selector switch after replacing the tempo lines. You really cant clean them because the rubber inside deteriorates and plugs itself up. Better to just replace it. Try bypassing it and see if she'll run.

 

[ape1972]

Thank you for the reply!
Would that fuel selector switch cause backfiring? I mean like major shotgun sounding backfires?

Thanks, Adrian

 

[mikidymac]

Flooding will cause backfiring.
Is it out the exhaust or intake?

 

[ape1972]

It's out of the exhaust.

 

[mikidymac]

IF there is no damage to pistons, then I would say it is flooding and there is fuel in the exhaust that ignites.

 

[ape1972]

I had just put new needles and seats. When i pulled the carbs they were clean. What do you recommend I do?

 

[ape1972]

No piston damage. 150psi in each

 

[esahlin]

Ive had backfiring occur because of low battery voltage to the MPEM. Even had it where the engine would start and run then die cause battery voltage to the MPEM dipped below 11 volts or so. It would start with a backfire though the exhaust then run a short time and die. The low batt voltage wreaked havoc on the spark delivery from the MPEM.

Not saying this is your problem but...…..if you have exhausted other avenues:
Check your battery voltage during cranking..... anything below 10.5 volts is bad and maybe even 11 volts or under.

My problem was the red wire from the positive batt cable that runs through the 15 amp fuse and then goes directly to the 4 point connector to the MPEM delivering the MPEM its batt voltage. The red wire somehow got loose in its attachment to the pos battery cable end inside the rear black electrical box near the battery. I cant explain it but the connection was loose and delivered all kinds of intermittent voltages to my MPEM stumping me for over 2 weeks.

Check the red wire voltage to the MPEM with a voltmeter under cranking etc. Check the red wire voltage at the 4 pin connector to the front grey eBox. Even follow it inside the grey box if you can.

 

[ape1972]

Awesome info!!! Electrical seems to me to be th culprit. Like I said earlier it ran great for ten minutes, died and then started to backfire. As soon as I get the motor back in I will follow up with you all.

All other suggestions are welcome.

Thanks guys

 

[ape1972]

The battery was new when this problem occurred.