Stock jets??

[sleddineinar]

Why does Yamaha put a larger (145) main jet in the #1 carb than in #2&3 (143.? I had truble last spring with #1 fouling the plug alot, since then I also discovered that the carb heater valve was removed by the previous owner (so that the heaters were always on). I bought a new heater valve and installed it yesterday. BTW, it's a 98 Vmax 700sx.

 

[xsivhp]

Has to do with exhaust flow and the one cylinder runs leaner than the rest. Heater valve shouldn't matter. Have you checked the choke plunger in your carb to make sure it's not stuck? I have a 1998 red head triple that has never fouled a plug. If it is stock, rejet it and re-clutch it according to the tech page and you will have a new to you sled. It makes a world of difference.

This is the exact setup I've got in mine:

97-99 SX700 Trail

51/43 Helix, stock weights w/4.5g rivet in 1st hole and 3.1g in tip, stock springs, (1 or) 2 layers removed from head gasket and 22/40 gearing. Jetting: 142.5 mains

It has been great and the sled is much nicer running than it was in stock form.

 

[xsivhp]

Here is a link to the page where I got that info. Hope that is of some help.

 

[sleddineinar]

Thanks, I've seen that page and I was going use those settings. I just took the carbs off yesterday to clean them, I took off the bowls to verify jets, they are stock. I just bought this sled last year so, I am discovering as I go what mods have been done. So far I can see, Reed spacers, 1 layer head gasket, & newer plastic skis & spindles, also a Red spring in the Secondary.

 

[sleddineinar]

When I follow the setup on the tech pages, and also drill out the stock can, and do the air box mod, should I still go with 142.5s in my mains or should I stay with the 143.8s?

 

[harness racer]

Fouled plugs on a red head are very unusual , i have built, re-built , ported and more for several years to this engine , and it would be wise to assume even if not so , that a cylinder that fouls plugs regularly is a indication of something to come , "leaky head gasket , seals, etc.. Have a good look ...

 

[maxdlx]

Leave the air box stock, if you mess with it it will be a nightmare to jet right. Maxdlx

 

[sleddineinar]

I wasn't completely sold on the air box mod, so thanks for the heads up.

As far as what harness racer said about, "leaky head gaskets, seals, etc." what should I look for in those areas, would the seal have any indicators to look at, ie, oil dripping? or what. I took off the heads yesterday, to look at jet wash, etc..

 

[sleddineinar]

I shot some pics with my phone (a little blurry), too show the piston jet wash. The piston is to the right on the photos of the block, on the photo of the head the #1 is on the left. I took one of each piston at TDC.