84 Sportfire

427cobra · Post by **427cobra** » Tue Feb 03, 2009 11:52 pm

Well after quite a bit of work this old sled is back and ready for the trails!! (almost)

It starts hard after sitting.(more than an hour) Starts right up after running though...

But with a shot of carb cleaner in the air tube it fires right up and runs good.

Has the gas shut off, new ball check in tank, new lines and clamps, new filters.

Like I said it runs really good (lifts the skis off the ground) and idles fine. Plugs look good as well.

The new gas cap did not have a vent hole...so when running the vacuum that was created caused the tank to suck in. I noticed this because the latch on the tank door would not latch...ha So I drilled a vent hole in the cap to take care of that problem.

The two things I can think of is to replace the fuel pump. There also isn't much gas in the tank and its not "fresh" gas.

Going to pick up a new exhaust pipe from Frankie. The one on there the mount is bent up.

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427cobra · Post by **427cobra** » Tue Feb 03, 2009 11:55 pm

Hand warmers installed! Nice and warm..

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427cobra · Post by **427cobra** » Tue Feb 03, 2009 11:59 pm

Just need to figure out this hard starting issue and I will be set....

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smitfire · Post by **smitfire** » Wed Feb 04, 2009 12:00 am

what else have you done, crank seals? i have this with my sportfire but it has to sit 3 or more days

427cobra · Post by **427cobra** » Wed Feb 04, 2009 12:04 am

Didnt do crank seals....hmm. I was told the engine had been recently rebuilt (within a year or two) I was also told it was ridden all last year with no problems.

427cobra · Post by **427cobra** » Wed Feb 04, 2009 1:35 pm

You guys think it could be the fuel pump??

S_Kyle · Post by **S_Kyle** » Wed Feb 04, 2009 3:02 pm

There could be a bit of material stuck in the pump. I would rebuild it if in question as the kits are only around $5.

ChickenRat · Post by **ChickenRat** » Wed Feb 04, 2009 4:28 pm

I recently went round and round with this on my '84 Sportfire as well. Exactly like yours, it would start and run but if it sat for an hour or longer and the damn thing wouldn't start. When it ran, it ran perfect. Also like yours, my motor had been rebuilt within the last 200 miles including the crank seals. I did the whole process of elimination thing. I cleaned the tank, new fuel lines with check valve, filters, put on a new fuel pump, checked the impulse line, checked my rubber intake boot, adjusted the choke(fuel enrichener), cleaned the carb more than once and I did all this one at a time so I could pinpoint what the issue was. After all this, it still did the same thing and I was a bit cranky. In the end, it ended up being an issue with the floats/needle & seat. I put in a new needle & seat and made sure the floats were moving properly and and everything was adjusted properly. Ever since then, it starts easily even after sitting for a couple of weeks and fires up warm easily as well. Keep plugging away at it and you'll figure it out.

Robb

427cobra · Post by **427cobra** » Wed Feb 04, 2009 7:50 pm

Robb,

Where did you get the correct needle and seat? Do you have a p/n for that?

Thanks!

ChickenRat · Post by **ChickenRat** » Thu Feb 05, 2009 12:01 am

Just went down to the local Yamaha dealer and they lined me up. Wasn't cheap however.

Robb

Post by **ICCSF 108** » Thu Feb 05, 2009 12:35 am

Eric, if you can't find one close let me know.. I have an extra for the 36mm carbs I think the 34mm use the same one??

Kenny

427cobra · Post by **427cobra** » Thu Feb 05, 2009 1:02 pm

Hey Kenny that would be great. Im not sure if the same was used on the 36 and 34's however.

If I remember correctly the one that is in there had a rubber tip on it. So its probably not the correct one.....

If I can get the correct mikuni p/n I could check out the local Honda shop..

Rodimus Prime · Post by **Rodimus Prime** » Thu Feb 05, 2009 3:01 pm

36 and 34 use different seats.

ChickenRat · Post by **ChickenRat** » Thu Feb 05, 2009 3:06 pm

Don't Honda's use Keihin carbs and not Mikuni's?

Robb

427cobra · Post by **427cobra** » Thu Feb 05, 2009 11:02 pm

Looks like they use the 1.5 needle and seat!

Thanks!