94 GTX possibly overheating

[laptop4079]

Yet another interesting problem in my new to me pwc. I just put a top end kit on my 650 and took it out to the water to begin to break it in and I'm being hyper aware because this has been my first rebuild. After a few minutes of putting around at idle I lifted the seat to feel the exhuast pipe and head, the head was getting pretty hot but the pipe was cold. My telltale is also pretty weak/non existent at idle but shoots pretty far if I blip the throttle. I'd be less worried if I knew if my overheat alarm worked but I'm waiting on parts to fix that. Should the cylinder head be almost to hot to keep my hand on?

 

[laptop4079]

Forgot to mention I have completely rebuilt the jetpump assembly with a new wear ring, neo seal and o-rings

 

[benjilafouine]

Seems like your exhaust is cooled but not the engine.

 

[laptop4079]

I would hook up your garden hose, and do a reverse flush, then you can verify that your air bleed is working, and you can flush out any debris that may be in the bottom of the cylinders, also check that your drain line isn't plugged.

It's a brand new top end kit so I don't think there's debris in the cylinders. I had the hose hooked up when I ran it breifly before I took it to the water to make sure I wasn't going to waste a trip everything was fine. Engine and exhaust was cool on the hose

 

[laptop4079]

I pulled my pipe off when I got home to double check there wasn't a blockage in one of the hoses or the brass inlet barbs and I remembered when I was going through my manual that those are metered for specific flow. Well in the manual it only lists one for my ski a "37" and my pipe has 2 one's stamped 22 and the other is stamped 18 so I'm kind of at a loss on what to do next. Does anyone have a 94 gtx that they wouldn't mind taking pictures of the exhuast for me?

 

[POPPS]

Is your drain line clear, is your cylinder head clear, it's rare for blockages there, but easy to check.

 

[AKnarrowback]

With the engine running pull the wire to the engine temp sensor and touch it to ground, if you hear the overheat horn then you know that works. You can always remove the sensor and heat that to test the entire system. Or just use an ohm meter between ground and the wire post on the sensor to check if the switch has closed indicating an overheat situation.

While you were driving it you say the tell tale shoots out pretty far and at idle it is weak, this sounds about normal. If anything I would double check the tell tale line for any blockages.

The motor is always going to run hotter than the pipe. If the motor gets too hot to touch then shut things down asap and investigate. Under normal conditions it is going to be pretty warm but not too hot too touch for the working hand, maybe a hair too warm for an average hand.

Being cautious is always a good thing with a fresh rebuild, especially if it is a first time. If you have access to a cheap "point and shoot" thermometer you can get head and cylinder temperatures off the motor. If I remember right the temp alarm is set to close around 205 F, motor temps below that are acceptable.

 

[AKnarrowback]

Pipe fitting stamps on my 94 gtx.

Top one above the mag (front) spark plug is stamped 18.

The lower fitting, at the other end of the hose on the upper fitting, that is on the rear "cone" is stamped 37. This is not an elbow fitting and finding the number took a flashlight and mirror.

The other small fitting, on the front of the pipe close to the battery, is stamped 24.

All are known factory OEM fittings, the machine has never been modified. Hope that helps. If the two upper fittings are painted the same purple as the pipe and don't show evidence/scratches of being removed I would guess those are factory installed and good to use.

Why did the top end get rebuilt by the way? The only time I have seen those fittings changed were when carb, pipe or engine mods were done.

 

[POPPS]

Apologies, I can't picture your water routing on that machine, if it was mine, I would remove any hose (including cylinder head, repeating myself here, sorry),that water runs thru, and use compressed air to make sure they are clear, and since your pump is serviced I might assume there is no stress on the motor from the pump.

 

[laptop4079]

Okay I have rigged an old trailer light to be my "overheat buzzer" until my replacement comes in the mail and boiled my temp switch to test it because I'm itching to get back on the water.

Pipe fitting stamps on my 94 gtx.

Top one above the mag (front) spark plug is stamped 18.

The lower fitting, at the other end of the hose on the upper fitting, that is on the rear "cone" is stamped 37. This is not an elbow fitting and finding the number took a flashlight and mirror.

The other small fitting, on the front of the pipe close to the battery, is stamped 24.

All are known factory OEM fittings, the machine has never been modified. Hope that helps. If the two upper fittings are painted the same purple as the pipe and don't show evidence/scratches of being removed I would guess those are factory installed and good to use.

Why did the top end get rebuilt by the way? The only time I have seen those fittings changed were when carb, pipe or engine mods were done.

Thank you so much now I know mine are not original! I do have a point and shoot temp gun I'll bring with me tomorrow. The top end got rebuilt because it lost compression and the pistons looked like swiss cheese. Look at one of my previous threads for pictures it was horrendous

Apologies, I can't picture your water routing on that machine, if it was mine, I would remove any hose (including cylinder head, repeating myself here, sorry),that water runs thru, and use compressed air to make sure they are clear, and since your pump is serviced I might assume there is no stress on the motor from the pump.

I blew all the lines out again today and even the passages in the pipe nothing came out and they're really free flowing. I'm not going to pull my head off again to check for sand lol those o-rings were a pain to get in there haha.

 

[AKnarrowback]

My concern is that the way the machine runs can be changed by the size of the water fittings on the pipe. Did you find the root of the problem that caused the motor damage? Did you go through and rebuild the carbs or at least take the time to clean them out and check them? Are you the original owner? Have you used this machine for enough time before the motor failed to know that the pipe fittings let the machine operate properly?

I just don't want you to destroy a new top end if the cause of the first failure us not known.

 

[laptop4079]

My concern is that the way the machine runs can be changed by the size of the water fittings on the pipe. Did you find the root of the problem that caused the motor damage? Did you go through and rebuild the carbs or at least take the time to clean them out and check them? Are you the original owner? Have you used this machine for enough time before the motor failed to know that the pipe fittings let the machine operate properly?

I just don't want you to destroy a new top end if the cause of the first failure us not known.

This is a new to me ski and my first 2 stroke anything. I believe I bought the ski with the pistons already hurt. The starter was really weak on it giving me the false impression of decent compression when I went to look at it before purchasing. When I got it I immediately put a new starter on it and rebuilt the carbs with cheap sbt kits(didn't check pop off or needles).I took it out and learned it cavitated real bad so I rebuilt the jet pump and it ran but only for about 10 minutes at a time and I was having trouble tuning the carbs and then one time it wouldn't restart and that's when I tore it all apart. I have no doubt I probably caused some damage with the pump cavitating really bad not pushing water through the motor and the wrong needle in it. Since then I've rebuilt the carbs again with real mikuni kits and when I went to put new needles and seats in it. I learned the ones in it were the wrong ones. It had 1.8's in it and I put 2.0's in it. Here's the thread with the pictures of my pistons Restoring a 94 GTX have an issue

 

[AKnarrowback]

Which main and pilot jets were in the carbs? What was the pop off set at?

 

[laptop4079]

Which main and pilot jets were in the carbs? What was the pop off set at?

I butchered the jets getting them out and couldn't read them, I should have replaced them to be cautious but I was going to examine my plugs after every step of breaking it in. Pop off was set at 24/25 I was trying to get it higher but every spring combo was either to high or to low or the differential between the carbs was to crazy.

 

[AKnarrowback]

Butchered jets are going to kill the motor before you have a chance to read the plugs.

If the jets are the wrong size they can also kill the motor.

If someone changed fittings on the pipe there is a good chance jets were changed as well since both are tools people use to gain more performance. However, if you have stock carbs, a stock intake and stock pipe there is no reason for anything pipe fitting or jetting related to be changed from stock.

 

[laptop4079]

Butchered jets are going to kill the motor before you have a chance to read the plugs.

If the jets are the wrong size they can also kill the motor.

If someone changed fittings on the pipe there is a good chance jets were changed as well since both are tools people use to gain more performance. However, if you have stock carbs, a stock intake and stock pipe there is no reason for anything pipe fitting or jetting related to be changed from stock.

When I say "Butchered" I mean I buggered up the flat head slot the actual jet hole hasn't been touched. I understand what you're saying though playing with the unknown. It has the stock intake and I believe the pipe is just off a different ski because it's not the stock purple pipe it has they gray one and the number on one of the brass fittings belongs to a 587 motor.

 

[POPPS]

I apologize, when I suggested checking the cylinder head, my intention was to remove the head and Split it, you will need to remove the Sparks first. My train of thought here is to eliminate any blockages in water delivery,, to the pipe, head, or cylinders.

 

[POPPS]

Regardless of the water pipe fittings,(they will not give you hot cylinders at idle and check that there are not carb jets in the fittings...they are meant to heat the pipe to scavenge fuel from the motor, and increase top rpm). I would set your carbs to the stock settings.sillly as it sounds, you may need a magnifier to read the jets, especially the pilot, which is very small. This will save you from trying to remove the pilot jet with rounded edges if it is proper.

Use your pop off gauge to test your carb for external leaks and then check your pop off pressure, since this will make the biggest effect on low end throttle response. However, this should not have any effect on your original issue, of the hot cylinder head, trust me, from years of racing, when engines fail, it is not at idle, assuming the water flow is normal...if your engine is not modified, the engine will fail from oil pump failure, (rare,), crack in the oil line, sometimes, or fuel starvation

Most common reasons are: usually at the fuel pick up, (bottom strainer), fuel selector, fuel lines, or carb micro filter. Or. Eventually, just metal failure in the Pistons, or crank.

 

[laptop4079]

Update time. Turns out I was probably just being skiddish with this being my first rebuild. I've been out here running it for about an hour with no overheat alarm and with cylinder temps in the 150-160's.