1997 GTI 717 won’t rev out

[Spraddad5]

Hello All,
New to the forums, hope you all can help. I bought a ‘97 GTI from a guy at work. It needed a top end. All done and back in the water. It has the newer accel pump style single carb like a ‘98. Carb is brand new. Problem I’m having is it idles perfect. On top end it seems good. The issue is the middle. If I punch it from a slow speed, it will just maintain lower rpms forever and not rev out. It’s not missing or cavitating, I’m mechanical enough to know I’m good there. If I slowly walk it up to about 1/2 throttle, then punch it, it stays at same rpms for about 2-3 seconds then pulls up to full throttle like a snowmobile. Like it’s hitting a powerband. It never bogs out and dies, just no throttle response. I’ve done the fuel lines, oil lines with tygon, and fuel filter. Fresh 93 octane fuel. Machined the rotary valve cover back to spec. I even put the old non-accel pump carb back in after a rebuild, and it was worse. Wouldn’t get to top end at all! I’ve unplugged the rectifier, nothing. PLEASE HELP

 

[POPPS]

Sounds like your midrange transition circuit is off,,,pull the carbs,,,clean every orifice,,,check that jets are stock,,,check popoff,,make sure its not too high,,,,make sure the pilot bypass holes are clear,,,
for large hesitations,,where ut almost wants to die,,,usually the popoff is too high, ,for low hesitation,,,it may need a larger pilot jet,
Turn the low out to 3 turns,,,( the biggest allowed by law by mikuni),,,and see if that helps,,,if yes,,,go bigger pilot,,,one size,,,if not reduce popoff.

 

[Spraddad5]

Sounds like your midrange transition circuit is off,,,pull the carbs,,,clean every orifice,,,check that jets are stock,,,check popoff,,make sure its not too high,,,,make sure the pilot bypass holes are clear,,,

Thanks popps I’ll start that tonight. What really got me was when I went through the stock (non accel pump) carb and put it on, it actually got worse. Any chance it could be a weak coil or bigger internal engine issue like a crank seal? And since the carb is the updated 1998 GTI version, I’m assuming the published ‘98 carb settings for jets and pop off are what I should use?

 

[Ckrawiec]

The carbs on the older doo's are real finicky beasts.....IMHO, I'd get the original carb back to factory specs.....Mikuni parts, new needle and seat, correct spring......follow the Carb Rebuild sticky post. 99.9% of the time your problem description goes directly to fuel delivery to the engine.....the carb always seems to be the key.

Clean the RAVEs too!

 

[Spraddad5]

Ok would you recommend going back to the original 1997 non accelerator pump carb? Or the the one with the pump. To my knowledge, the one with the pump is what Mikuni would send me if I ordered a new carb for that model seadoo. As they don’t make that older version anymore. I have both in my garage.

 

[Lothsahn]

No need to order new carbs. A rebuild kit and a thorough cleaning should do it, if done as described in the sticky thread.

Can't speak to whether retrofitting an accelerator pump is a good idea, but it should definitely run well with the original carb. Only issue is long periods of idling can cause it to load up without the accelerator pump. I was actually considering looking into retrofitting an accelerator pump on my 96 GTX, but no idea if that's a good idea or not.

 

[mikidymac]

It really depends but the rebuild with all new Genuine Mikuni parts is the first step.

I know these carbs inside and out and the one on my wife's 2003 GTI just wouldn't run correct no matter how many times it was cleaned and rebuilt it would bog around 1/4 throttle. I finally admitted defeat and replaced the carb with a brand new Mikuni and it has never run better.

 

[Spraddad5]

I’ve got a mikuni kit on order. I’m gonna start with the original 1997 carb at factory settings and pop off with a new full rebuild kit. Thanks for the replies.

 

[POPPS]

Apologies,,,i just edited my previous reply.

 

[Spraddad5]

Ok. So I did what we talked about. I went through the exhaust. No collapsed tubes, no broken baffles. Put the original 1997 carb on. At factory specs per the service manual. With a mikuni kit. Spec is 1 3/4 turns out on LSN. Zero on the HSN. Set pop off dead on spec at 33psi with a precision regulator tester I built. Pop off was at 21 psi when I tested before this rebuild. Checked the timing of the rotary valve. Ok. Now, here is one thing I found….the previous owner had the head cooling lines swapped. The line coming from the hose adapter by the jet was going to the “in” side on the head. The line coming from the “pressure zone” fitting was on the “out” side of the head. All other water fittings look correct. Could this cause any of these bogging/exhaust pressure issues? I’m headed to the lake in the morning for a test ride. Fingers crossed.

 

[Spraddad5]

Update: just back from the lake. No change. Ive tried everything with this original carb. The service manual settings are 1 3/4 out on the LSN. Zero on the HSN. Settings found on Seadoosource.com are 1 turn out on LSN and 1 1/2 out on the HSN.
Neither of these worked. If I can find a way to feather, choke, baby the ski up to 3/4 throttle, the top end is good and strong. It just flat will not transition from idle to WOT. At one point, I was able to pull the choke out a little and hold it steady, and it pulled from 1/4 to wot like it’s supposed to. Like it just won’t pull fuel. The accel pump carb was still better so I guess I’ll back to that carb and start over. Any idea guys? Could it be a deeper engine issue like a crank seal or something? Thanks