Carb Issues

[etemplet]

Today is the day. the 96 GTX carbs are coming off for a check and replacement of Needle and seats with genuine Mikuni Parts and... the black spring. I'm gonna record the changes in pop off just by installing the factory stuff. I'm pretty sure pop off is at 23psi on this ski which is the bottom of the range. Personally I believe numbers this low contribute to the engine running rich in the lower RPM range. This may not always be the case but the other GTX bottom end got more crisp and responsive. No arguments... just reporting. Stay tuned.

 

[etemplet]

Okie Dokie, had a very productive day with the jet skis. Not sure what the end result will be performance-wise but I am looking forward to a test runs tomorrow.

Both carbs... popped off at 16psi and had a difficult time reseating and holding pressure (wouldn't do it). I could not identify the size seats and needles. I put a Mikuni Carb kit in this ski over the winter but being new to skis didn't yet have a tool to check the pop-off. More importantly, I installed the mikuni needles and seats (1.5) and the black (80 gram) spring. I also took the carbs apart and gave them a good once over doing my best to clear the 3 small holes in the barrels.

The result of changing the needles and seats to mikuni and installing the black spring put the Pop-Off at 37 pounds on both carbs. I was going to shoot for 30-32 psi but, I'm not touching these babies. Install is done. I'm thinking I might have it this time. LOL This should lean the carbs out a bit which would help.

When I starter her up... she sounded pretty freakin mean.

 

[GGuillot]

I'm in the middle of going through the carbs on my 97' GTX, reaching final stages and I'm ready to start. Total disaster in these carbs, where did you pick up the black spring? Mine appear to have a silver springs.

 

[etemplet]

I'm in the middle of going through the carbs on my 97' GTX, reaching final stages and I'm ready to start. Total disaster in these carbs, where did you pick up the black spring? Mine appear to have a silver springs.

I ordered the springs from Bay Area Power Sports in Virginia. . On this forum there is a site that has all the numbers of the springs and colors. Back is 80 gram and the one that is supposed to be in the carbs. I am looking forward to riding the skis today. Good Luck. Make sure you get some liquid out of those 3 little holes in the barrel.

 

[kmarts]

Watching this thread for an update.

I'm having similar problems to you, although you seem to have resolved most except your flat spot before the raves open, If you pop it out of the water it will take off...I also have this problem but until i solve the low end I'm not even bothering with it.

For your consideration there was a TSB on certain 97's concerning the exact problem we're having. The solution was to install slotted rave valves and updated housings.

 

[etemplet]

Watching this thread for an update.

I'm having similar problems to you, although you seem to have resolved most except your flat spot before the raves open, If you pop it out of the water it will take off...I also have this problem but until i solve the low end I'm not even bothering with it.

For your consideration there was a TSB on certain 97's concerning the exact problem we're having. The solution was to install slotted rave valves and updated housings.

Great find !! on the rave valve issue !! I had a few to choose from and I believe I used the ones without the groove. I'll have to check. Problem I will have is that the cylinder bore size is 1mm oversize. I was very meticulous in getting tight clearance on the piston and rings. I wish I had kept the old cylinder and piston now. It worked great for measuring and grinding and fitting.

I am ordered new housings but in the meantime may repair mine. I definitely got my wife's 97 kickin but the 96 pulls her about 2 lengths while she transitions. My GTX doesn't have the spunk up top. I rebuilt all the raves on both skis but the Mag cylinders on both have oil leakage. I attribute that to wear on the valve guide. I recently pulled the raves on both skis and had a look.

Guess I'm gonna break down and do a compression check on mine. LOL

 

[etemplet]

On the carbs... took the skis out today and I gained 120rpm up high after the mikuni needle seats and spring. As expected the high pop off affected my low speed but I wasn't ready for a lean bog. After a warm up and a couple of hole shots the hesitation was minimal but still there. I can back after 50 cruise with my wife on her ski. She is still faster. I opened the high speed adjuster on the PTO carb 1/4 turn and about 1/8 turn on the Mag (dang that was difficult to get to). I lost 120RPM immediately. So.... jetting is still fat. How fat? I don't know. I will look at the plugs tomorrow. I expect them to look really good so I am most likely done with these carbs unless I can't adjust the off idle hesitation with the low speed adjuster. Pop off might just be a little high at 37 but everything is mikuni so I am not gonna chase this around much more.

On this ski, the 96GTX, I am going to look at the water valve closer and spend some time on the raves. That will be about all I can do. It hit 50 on the GPS today. Tach 6630 or 6640 no sure which. I don't trust the tach numbers but... that's all I am showing. In the spring I saw 6800.

I was asking my wife today, "How many people would be satisfied with the skis and just ride them?" Most... LOL

 

[kmarts]

On the carbs... took the skis out today and I gained 120rpm up high after the mikuni needle seats and spring. As expected the high pop off affected my low speed but I wasn't ready for a lean bog. After a warm up and a couple of hole shots the hesitation was minimal but still there. I can back after 50 cruise with my wife on her ski. She is still faster. I opened the high speed adjuster on the PTO carb 1/4 turn and about 1/8 turn on the Mag (dang that was difficult to get to). I lost 120RPM immediately. So.... jetting is still fat. How fat? I don't know. I will look at the plugs tomorrow. I expect them to look really good so I am most likely done with these carbs unless I can't adjust the off idle hesitation with the low speed adjuster. Pop off might just be a little high at 37 but everything is mikuni so I am not gonna chase this around much more.

On this ski, the 96GTX, I am going to look at the water valve closer and spend some time on the raves. That will be about all I can do. It hit 50 on the GPS today. Tach 6630 or 6640 no sure which. I don't trust the tach numbers but... that's all I am showing. In the spring I saw 6800.

I was asking my wife today, "How many people would be satisfied with the skis and just ride them?" Most... LOL

As far as i know your MAG carb High speed should be closed, the stock jetting is sufficient up top. But the PTO carb has a tendency to run hotter which is why it's the one adjusted a quarter turn if needed.

So Far I've done pretty much what you have, replaced everything in the carbs with OE parts but have problems with the thing wanting to fall on its face just off idle. Been through the carbs like 4 times just like you, didn't realize just how badly plugged the pilot circuit can get.

But the last time out I was having problems with inconsistent idle and when on the hose if you rev it up it takes a long time to come back down on it's own so I'm thinking I may have an air leak somewhere. Finally got some aluminum plate yesterday to make block-offs. Hopefully can get at it this weekend.

 

[etemplet]

But the last time out I was having problems with inconsistent idle and when on the hose if you rev it up it takes a long time to come back down on it's own so I'm thinking I may have an air leak somewhere. Finally got some aluminum plate yesterday to make block-offs. Hopefully can get at it this weekend.

Sounds like we might be in the same place on the carbs. I have to look at the spark plugs but I'm sure they will be good. The engine's reaction to opening the high speed proves I'm getting enough fuel on top end. For the low speed stumble... which I now have since I installed the OEM Parts (pop off 37psi) I am going to give it more fuel on the low speed adjuster to see what happens. I know lowering the pop off to about 32 will address the stumble but not sure how much. At least now I am at the point where I can see changes are happening. Previously, it was rich, more rich, and less rich. LOL I've tuned 2 strokes and know doggon well it needs a smaller main jet but I like the safety factor of the larger jet. Don't wanna melt anything for a couple MPH. LOL

As high as the pop off pressure is, it may not respond to opening the low speed adjuster. It may be that the needle just isn't letting the gas through because it is set so high. I am going to order a range of mikuni springs. They sure are proud of those damn things.

 

[kmarts]

Sounds like we might be in the same place on the carbs. I have to look at the spark plugs but I'm sure they will be good. The engine's reaction to opening the high speed proves I'm getting enough fuel on top end. For the low speed stumble... which I now have since I installed the OEM Parts (pop off 37psi) I am going to give it more fuel on the low speed adjuster to see what happens. I know lowering the pop off to about 32 will address the stumble but not sure how much. At least now I am at the point where I can see changes are happening. Previously, it was rich, more rich, and less rich. LOL I've tuned 2 strokes and know doggon well it needs a smaller main jet but I like the safety factor of the larger jet. Don't wanna melt anything for a couple MPH. LOL

As high as the pop off pressure is, it may not respond to opening the low speed adjuster. It may be that the needle just isn't letting the gas through because it is set so high. I am going to order a range of mikuni springs. They sure are proud of those damn things.

All i can say is be %100 sure the pilot jet holes are clear. I hate to admit it but I thought mine were good and they weren't. I've cleaned and rebuilt an assload of carbs so was probably a little arrogant about it (this is my first sbn carb).

At first i didn't' know about those 3 pin holes so didn't think to check them the first time... They were definitely plugged. Every time i went through the carbs I saw improvement in flow of carb cleaner when sprayed through the low speed circuit, again i was hurrying and being impatient obviously.

Not until this last time did i leave the LS needle in while spraying through the pilot jet port then blasted them out with my air compressor @150 PSI and now I feel like I'm getting %100 proper flow. But now i have everything apart because i might as well leak test the engine just in case, I'm not close to the water so I don't want to have to make a test trip again lol.

 

[mikidymac]

Also keep in mind at some point the carbs can't be completely cleaned in all the little holes if there is corrosion and you just have to admit defeat and buy new carbs. After doing carbs on these for 25 years I finally gave up and bought a new carb for the Wife's GTI and it has never run better.

 

[etemplet]

All i can say is be %100 sure the pilot jet holes are clear.

They are miserable to clean and prove they are clean.