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1997 GSX Slow to rev down

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kmarts

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So This has been an ongoing thing and am at the point where I'm out of ideas, looking for opinions.

My 97 GSX when running on the trailer, if i blip the throttle she revs up and seems to take her sweet time coming back down. Eventually it does but it's no where immediate, like 10-20 seconds.

Last time i had it on the water i noticed that if i was riding on plane and just let off the gas it would hold around 2200-2300 RPM for 10 seconds before dropping to a normal ~1400 RPM Idle.

Motor does not run away

As far as the fuel system goes this is what I've done:

Rebuilt carbs including needle/seat and new black spring (pop-off~30psi on both), all genuine mikuni parts
replaced all grey fuel lines
Cleaned fuel selector
I even went over the carbs a second and third time making sure those 3 tiny hols from the pilot jet are clear.
New plugs
Clipped plug wires back

Other than that the thing runs well, I've hit 6700rpm in not the greatest water conditions. Does have a bog just off idle, but i changed the needle and seat last week in hopes that they may have been the cause... Haven't had a chance to run it since so i don't know if it's still happening.
 
I would make sure your throttle cable has a little play in it and it isn't holding the carb open.
 
Should be 2mm.
You can also try turning the low speed screws out 1/8 turn at a time and see if it gets better, it could be a little lean.
 
so i have enough slack in the cable. Don't have time to mess with the LS screw until the weekend.

Something potentially related:
Does the PTO carb butterfly sit more open than the mag carb without the linkage arm attached?

I have a spare RV cover on the bench and when i had the carbs out i bolted them up to it, no linkage arm attached and held them up with a fluorescent light behind them. PTO carb butterfly was slightly ajar where the MAG carb was closed completely. Is that normal?
 
Nope, with the linkage off and the idle screw backed out they should both be fully closed with no visible light. You might have a bent butterfly.
 
I haven't taken the carbs apart yet to check out if that butterfly is bent but I spent the weekend at the cottage playing around and I'm getting a little frustrated here...

First, it's hard to start cold. After starting you have to fiddle with the gas to get it to run... Mostly after you get it to fire cold then go full throttle it will stay running. Feels loaded up, takes like 5-10 seconds to clear out and will then begin accelerating.

If you just finesse the throttle (1/4-1/2) after starting cold it just wants to die.

Then, after you manage to get it out of the hole she'll run 6600-6700 rpm on the top end. After it gets warm the ski has a hard time getting over 5000 rpm holding the throttle wide open. I've read that there was some service bulletin for 97's needing slotted raves to overcome this. Mine does not have slotted raves, but I'm not even sure that this is the problem at this point.

When riding around if you want to do like 180's or quick tight turns, it won't accelerate well after slowing down and often won't go over 4600-5000 RPM holding throttle wide open. If i hop it out of the water while this is happening the motor will then spin up to full RPM.

Originally I had left the LSA's at 1 turn out, i then went 1-1/4 out because of the slow rev down on the trailer and the plugs looked too pale to me. I re-adjusted the idle in the water to 1400, synced oil pump and went on my way. Ran more or less the same and rode it for the afternoon. I didn't experience the slow rev down on the water that i did before.

Then on Sunday all of a sudden it wouldn't idle below 2200 rpm in the water...at all. So i just took it out of the water for the rest of the weekend. When i removed it from the water i started it to purge what water i could from the exhaust and of course it ran at a high idle.

Tuesday got home and started it to blast out any remaining water before putting it in the garage and it idled low. If you touched the throttle it wanted to die, now seems rich.

Tested compression last night just in case, both cylinders are around 140psi cold.

Like i mentioned before I've replaced everything in the carbs with OE parts and pop off is within spec. Now with the inconsistent idle I'm wondering if i have an air leak somewhere?

Not sure where to go next other than rip the carbs apart AGAIN to make sure i didn't miss any dirt.

Other question is, if the PTO carb butterfly is bent... Would the carbs being out of sync possibly be causing my problems?
 
I'd go with the vacuum leak somewhere, the inconsistency with the idle is an indicator. Check anywhere there's a screw going on the engine, according to the service manual everywhere on everything either loctite or sealant is used, Was there a rebuild at some point? Using permatex RTV instead an anaerobic sealant, like three bond, yamabond, etc could be an issue where the oil/gas breaks down the seal of the cases.
 
GGuillot said:
I'd go with the vacuum leak somewhere, the inconsistency with the idle is an indicator. Check anywhere there's a screw going on the engine, according to the service manual everywhere on everything either loctite or sealant is used, Was there a rebuild at some point? Using permatex RTV instead an anaerobic sealant, like three bond, yamabond, etc could be an issue where the oil/gas breaks down the seal of the cases.
Click to expand...

It has an unknown history to me. I bought it last fall from a guy who couldn't figure out why it was running away from him on the trailer. I found a stripped intake cover bolt thread that wasn't allowing the PTO carb to seal... After fixing that it doesn't run away anymore.

It's very possible the top end has been rebuilt, the head bolts don't have the white paint on them and look new. Anything I've take apart I've loctited/sealed as per the shop manual. I have no reason to suspect that the case was ever split, but i know using the wrong sealant would break down.

Trying to find the time to make some block off plates to do a pressure test but also trying to avoid potentially pulling the engine.
 
I wasn't able to make block off plates for a pressure test this weekend but hope to get to that soon.

Found a busted water regulator spring so I'm waiting for that to come in before i try to run it at all.

In the meantime I have a couple questions.

Is the rotary valve cover o-ring re-usable? I had to swap covers due to that stripped bolt hole i mentioned previously, the o-ring looked ok to me but maybe i should have replaced it?

If i have leaking crank seals... Inners would cause more than normal smoke, but this wouldn't cause a lean condition correct? Would outter seals visibly leak oil? and a leaking outter would cause a lean condition in one or both cylinders?

Thanks.
 
I wouldn't recommend reusing that o-ring as an air leak there is bad.

Inner crank seals will leak oil and smoke, especially after sitting.

Outer ones will suck air in, not typically leak oil out.
 
So engine builds no pressure... I made a plate for the exhaust and one for each carb opening. I also can't hear a leak... Before I pull the motor would it be safe to turn the pressure up in hopes of hearing where it's coming from?
 
My 97 gsx was slow to rev down. The butterfly’s weren’t in sync on the carbs. I’m not sure if that makes any sense but I synchronized the carbs on an extra intake and that fixed it.
 
That was actually one of my concerns but with everything blocked off and regulated air injected at 5psi the engine doesn't build any pressure so I have an air leak somewhere.

My question is can I turn up the regulator to try and hear where the leak is coming from and not risk damaging any other seal.
 
You can do the ether test. Spray ether around all seals and fittings. If you hit the right spot you will hear the engine change
 
So I turned up the regulator anyways until it held 5 psi constant.

Confirmed PTO outer seal is leaking.
 
Oh I know... This isn't my first rodeo lol. What I'm not %100 on is aligning the engine afterward, don't have the tool and honestly not likely to buy one. Any dyi hackish ways to do it?
 
Sorry, I am in Laughlin actually riding my skis for once. Your engine needs to hold 8 psi for a minimum of 10 minutes use soapy water to find the air bubbles. But since you found the leak I would get a complete WSM gasket kit from PWC Muscle and a tube of ThreeBond 1211 for the cases.

There are no DIY hacks for alignment, you have to use the tool or risk stripping the driveshaft, PTO and impeller.
 
so a question on this leak... It gets worse/better depending on the position of the crank. With pressure on (5 psi regulated to the leak), if i rotate the crank it goes from complete blowout to a slow leak.

Now knowing the seal is bad, what are the odds the crank could be twisted? is there a way to test?

You trust wsm gaskets?
 
Should just be a seal, your crank would have to be ridiculously bent for that to be the cause.
I have been using WSM kits for 25 years without a single air leak or failure.
 
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