Engine issue and fuel pump queston

D

Dcf1999

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Nov 12, 2012
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32
Age
43
Location
Dekalb, IL
I'm getting my sled ready for the season. About a week ago, I start up my sled and it runs well. I even drove it a little (10 feet to the other side of garage). I then changed plugs, chain lube, and checked the bearings. Try starting it again and now, for some reason, it runs like crap. It will only start on full or half choke. It wants to die on choke unless you feather the throttle. As soon as you take the choke off, it dies like it's starved of fuel. You can't even feather the throttle to keep her running. I'm thinking it's 1 of 2 things.

1) carbs sucked something in via air or fuel restricting one of the passages, however, if only 1 carb did this, would It cause that much of an issue with performance?

2) Fuel pump took a dump.

Because it dies when choke is switched off, I'm leaning toward a fuel pump issue. If only one carb is gummed up, I'm thinking it would still run with choke off just really crappy. I don't know, maybe it's something else even... vacuum like from engine? Any test I can do to rule out components? Pulled the plugs after trying to run and they are wet... so there is fuel getting into engine.

What do you guys think?

In regards to the fuel pump, is there a rebuild kit for them? I hate to buy it new from Yamaha as it's $100. I find Mikuni 3 output fuel pumps on Amazon for like $30. Can I just replace my fuel pump with one of those or do they have specific fuel output specs that need to be matched?

Sled is a 97 700 SX

Thanks everyone for your help and sorry for the long post.
 
Sounds like a ethenol issue or water in the gas I would take the carb rack off and make sure you don't have little white blobs in there clogging you jets had that on my old 02
 
Yea I'll go ahead and start by cleaning the carbs. I'll also pull the tank and clean it.... I should probably replace the fuel lines too since I'm going this deep into it.

What about the fuel pump... is that something I shouldn't worry about? It's as old as the sled so it kind of makes me worried... Are they that reliable?

I really don't want to pay $100 for a new one from yamaha and was thinking of getting an aftermarket Mikuni for $30 and throwing that in there. Will that work?

I could buy a used one off ebay but then i'm in the same boat with an old fuel pump lol. I wish I could just buy a re-build kit for it but can't find one anywhere. I hate when you know they make the parts to make a rebuild kit, but don't off it. I mean they obviously make the internals for a new pump, why can't they just sell them? Anyways enough venting...

Also... anyone know where I can download a service manual for the 97 700sx? I have one for my 600SRX and kinda been using that since the sleds are almost identical.
 
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My sled did basically the same thing. When I took my carbs off. I had 2 pilot jets that where plugged up. I also wondered about the fuel pump. But I left the fuel lines off pulled the rope. I had fuel coming out of all 3 lines. So going with the pump is good.
 
O2viper700 said:
Check what others suggested. If it does end up being the fuel pump I have one for you.
Click to expand...

Is it new or used? If used, what year sled is it off of?

The reason i wanting to replace the fuel pump is because it's 14 years old and if i have the carbs off, it's right there to change also... and pretty easy to change. I just don't want to be riding on the trails and all of a sudden it craps out... I really don't know how reliable they are at that age... Like I said... I'd rebuild it if i could find a kit... but you can't find anywhere. That's why I was wondering if I could throw an aftermarkey Mikuni ($30) instead of a yamaha one ($100). I would want to do it to my other sled also (97 Vmax 600 twin). The one thing I worry about with a used pump is that... well... it's probably old as well and will I have to worry about that one...

I'm going to pull the carbs either tonight or monday and should have her back together by wednesday... I'll also test the fuel pump right away after I pull the carbs off....
 
I wouldn't worry about the age of the pump. My sled is also a 97 sx 700. I also have two 91 cats. They both have the factory fuel pump. I have not had a problem yet with them. I say if it works go with it. Just my 2 cents.
 
sounds stupid, make sure you have enough fuel in the tank. and take the air box off and bleed the carbs via the drain screw on the float bowl. then try it, if not proceed to cleaning them. i dont think it would be a fuel pump problem, but stranger things have happened.
 
Sounds like your fuel pump would be good to go one thing I did do this year on my sled is change to fuel filter in the tank. I know it's going over board but I did it for piece of mind.
 
As others have suggested - your pilots are plugged. I wouldn't spend any coin on anything until you pull and clean the carbs. F/P rebuild kits aren't available because there isn't a market for them.

Yes, they are typically that reliable even decades old.
 
Yep. I don't even start my Viper till I've THOROUGHLY cleaned the carbs. You can't half *** clean these carbs, the pilot are small and don't forget about the screen assy's under the inlet needle. One tool to get the pins out of the float towers...... spring loaded center punch.
 
Cleaned carbs yesterday, will test later today. One question... What is the float hight supposed to be? According to my 600xtc manual, it's supposed to be 11.3 - 15.3mm... is that correct?
 
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Replaced fuel filter and all fuel lines. Put everything back together and it ran like a top.... Thanks everyone!
 
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