97 Speedster Carb Clean or "Rebuild"

[Fat Tony]

So, I have a miss on my port engine when trying to get up to speed. It will sputter for a moment or two not climbing above 4500 rpm, and then it will finally surge up to about 6200. it did this a few times and then it basically would not rev at all, would want to die if cracking open the throttle. Granted this boat sat for a year or so, and I have run about three tanks of fuel [premixed] through the system, but it just started doing this the last time I was out. The engines have less than 60 hours on them, as they are premium rebuilds from fullbore. I am fairly sure that it is a carb issue, maybe some junk picked up from the tank and some of the old gas I was unable to get out of the system, or debris from sitting for so long [and apparent lack of maintenance from the previous owners]...

So, the question is... pull the carb out and soak it in is a carb cleaner solution, or do I break it down a do a rebuild? I'm not sure I want to be the one to attempt the rebuild, but if so, what kit would I need. I am having a bit of trouble determining which Mikuni kit to buy for these carbs as they seem to be a different size than the previous/later years.

If rebuild it is, then I am wondering what it would cost for me to ship them out to someone like Waterluvr to rebuild it? If I do one, I may as well do the other, I think. I have already put a small briefcase of money into this basketcase, so now the wife is starting to watch the expenditures and need to be able to keep the spend tighter than just tossing money at it...

Recommendations?

 

[hotrodssnova]

I would pull the carbs and clean them first. I just bought a 94 ski that was all original down to the gray fuel lines. Everything was packed with crud and varnish. Pulled them all apart, good cleaning, put them back together, and worked like new. Doing it that way might work, but you might also find issues inside the carbs that need replacing. It's a pop shot either way.

 

[Fat Tony]

Thanks for the input. I pulled the carb today to check it out. Still has the original grey lines as well.... its a bit dirty externally but inside does not look that bad. The filter had a little crud in it though. I will still need a parts kit for new seals and whatnot, any idea which kit for my carbs?

 

[hotrodssnova]

Check the brass inlet and transfer tube on the carb itself. I ran solder and bailing wire to get a path for the cleaner to work.


Edit. ....
I've read here that the factory parts are best for the carbs. But, I will be watching for replies. I have 6 carbs to rebuild this winter.
4 on the boat and 2 on the ski.

 

[robing]

http://www.sea-doo.net/SHOPMANUALS/JETBOATS/2003/jet_a/lmt2003-001af.pdf

 

[FinnExplorer]

Thanks for the input. I pulled the carb today to check it out. Still has the original grey lines as well.... its a bit dirty externally but inside does not look that bad. The filter had a little crud in it though. I will still need a parts kit for new seals and whatnot, any idea which kit for my carbs?

You sure the lines are grey, or just some mold and stuff in it. Read from here on the forum that boats didn't come with Tempo lines, USCG regulations. Of course replacing old fuel lines is not a bad thing.

 

[Fat Tony]

Single carb per engine. Yep, lines are 100% grey... It's hard to tell in the pic, but they are certainly grey

 

[Fat Tony]

Ok, another question... I'm getting conflicting info on the pop-off pressures... In the specification manual it calls for one set of pressures, but in the shop manual for the same year is a higher pressure spec???
The second image says 36-40 FYI....
My pop off pressure is happening around 43psi, with the spring that was in the carb... Also a new needle and seat were installed.

 

[Dr Honda]

OK.....


it's really not conflicting. The first is 48 +-12. So that covers 36~40.

Second... the new needle and seat.... was it the same size? Was it an OEM Mikuni?? If it was an aftermarket... the pop-off may not be right. And... did you re-use your old springs, or did you replace them? Were the new springs OEM?

Basically... with the exception of the gaskets... all the aftermarket kits, and parts SUCK !!!!!!!!!!!

 

[Fat Tony]

All OEM parts. The spring I installed was the spring that was originally in the carb, the long silver spring. I'm not sure if my kit intended to include a black spring or not, but there wasn't one in the kit. Again, all OE Mikuni packaging.

 

[Waterluvr]

What size needle and seat are you using?

 

[Fat Tony]

I'll have to double check, but it should be a 150

 

[Waterluvr]

I'll have to double check, but it should be a 150

Figure out what you have in there and I'll get you some straight answers to sort it out.

 

[Fat Tony]

Thanks.... I'll get additional info when I get off around noon

 

[Dr Honda]

I'll have to double check, but it should be a 150

that would be a 1.5. (lol) BUT... a speedster with 720's would use a 1.2. (But let me double check that)

 

[Dr Honda]

do you have a single carb with an accelerator pump?

 

[Fat Tony]

that would be a 1.5. (lol) BUT... a speedster with 720's would use a 1.2. (But let me double check that)

Whoops... UR right LOL... had compression test numbers in my head, which are 150 per cylinder [tested]. Yes, the old and new are 1.5.... yes, I have twin 720's with single carbs and a small secondary pump attached, i'm guessing that is the accelerator pump?

 

[Waterluvr]

1.5mm N/S's are correct for your application on the '97 Speedster, use an 80 gram spring (black) and run 182.5 main jet and 67.5 low jet with the low speed adjuster out 1 1/4 turns.

Seat the high adjuster and back it off half a turn so you have a visual reference point, from there to 1/4 and then again to an 1/8 and split that in half for about 1/16 of a turn total open to add a little bit more fuel to the bombsight at WOT and help keep the cylinder temps in the pto end down.

 

[Fat Tony]

ok... thanks.

 

[Dr Honda]

Yep... the single carb 720's used the 1.5 N/S.

I would get it on the low side of spec. Set it to 36~38, and it should run.

 

[MLars]

I'll try to add what information I know from going through this whole process. Carbs can be a pain, and to get it dialed in correctly I wouldn't let anyone other than a professional touch mine. The grey lines on the carbs have special restrictors built in, and are not meant to be replaced by any standard fuel line. Some carbs don't even need any new parts, just a good cleaning to get rid of all the old crap. Once again, a professional will have the correct tools for this. I had mine done by Waterluvr, and to be honest if I tried to go through them myself I probably wouldn't have gotten my boat running. He just found so many minuscule errors that would have caused headaches down the road.

 

[Fat Tony]

Thanks for your input MLars. I would love to have a professional carb builder do mine, but right now, the wife is watching my expenditures on the money pit (as she calls it) ... I am a CNC/Machine technician/maintenance tech for a living, and a pretty competent mechanic, so I am used to dealing with rebuilds such as this. I just need the correct info, and that has been my bane. This year seems to have a slightly different carb than the pre and post 720's, which has made it difficult for a non rotax/seadoo person such as myself to know what parts I need.... Something I have learned is just contact the right vendors and they will take care of you

 

[Fat Tony]

Ok... another question... is there a PN for the accelerator pump hoses? I found a tiny split in one of mine and want to replace them all....

 

[Fat Tony]

After an exhaustive 2 hour search through dozens and dozens of threads I think I found an answer... I went ahead and ordered some 1/8" ID x 1/4" OD 1/16" wall yellow Tygon. I will be sure to remove the old restrictor tubes from the old hoses and install them in the new hoses.

 

[Fat Tony]

Ok, so my fuel line arrived today. I took off the old grey lines and cut them in half length wise expecting to find restrictors in one of the lines from each carb.... nope. Neither carb has restrictors in either of the lines. Is it a definite that all years, all carbs had these flow restrictors?