Yamaha Jetting size's?

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Floader

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Hello, Just got my first Yamaha (had everything else, but mostly Cats) its a 1999 SRX 700. It was supposed to all stock in the motor area, but on inspection it has V-force reeds and looks like the air box is gutted. it also has really good compression for a 4500 mile sled, 140 to 145.
Went to clean the carbs and it has bigger than stock jets? I dont get the jet numbers on this sled, its got 151.2, 151.2 and a 152.3. How big of a jump is that over stock and how does that compare to regular mikuni jets (i.e. 440 or 450?) what is the .2 mean? can sombody explain this? Thanks
 
The re-jetting is likely because of the airbox. The jetting comes staggered from the factory. Also, that compression is pretty high, so it has likely had the heads shaved or used thinner gaskets or both.
 
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Those are standard small round main sizes. Not sure how they cross with the hex sizes, but the way these go is 145, 147.5, 150 152.5, etc... Then they have a half size in there which is what you are seeing with the 151.3.
 
stock for that year is #s 1/2 146.3 #3 148.8 youre up about 2 jets sizes (as far as the compared to normal mikunis# i don't know the comparison, someone b etter with carbs will probably chime in)
x2 on the compression, gauges can vary but thats up there, i'd say somethings been done as ryan stated
 
THESE CARBS ARE COMPLETE DEFFERENT THAN THE ROUNDSLIDE CARBS YOUR REFEREING TO THAT ARE ON 10 SIZE INTERVALS. THE NEW TM-X FLATSIDE CARBS CAN BE JETTED EXTREMELY CLOSE IN SIZE ALL THE WAY INTO THE 160,s TO THE 120,s. THAT SLED IS NOT STOCK, THE STOCK JETTING FOR A 99 SRX WAS 148.8 146.3 146.3 3:16 (yammie tony)
 
Thanks for the help guys, I got this thing for cheap and just wanted to have a reliable sled to bang around on the local trails on, its kinda turned into a complete mess/money pit and now i find out the the motor isnt stock. Guess ill pull an head off and see what the deal is.
 
One thing about Yamaha triples is that they use smaller bore carbs. This increases the air velocity through the venturi, which often results in a smaller jet size.

Unless it has something wrong, or you have reason to believe that it is jetted wrong, I would run it as is (after cleaning of course). That sled can be very reliable even after those mods. Watch your plugs and piston wash.
 
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It maybe that it is setup properly, but you never know, I just wanted to get an idea of where i was starting from. The sled has suffered from a sever lack of maintenance from the guy I got it from, who didnt know anything about it.
 
I agree with the above. Until you run it, who knows if the jetting is on? I would do all the necessary maintenance, and then take it out and read the plugs several times, bottom, mid, and top. Altitude and temp play a big role, of course. As far as dependability, I've never believed that doing some mods to a sled somehow makes it less dependable than stock, if attention is paid to getting everything set up correctly after mods are performed. Every sled I've seen that isn't dependable, all four brands, as always been from owners that put in gas and pull the cord, no maintenance. You seem to understand the importance of this, from what I've read. Just don't let the fun of going out on that first ride keep you from performing several plug checks. I would have the mind set that the first ride is going to be "sacrificed"(I kind of enjoy it!) for checking and tuning. If you have to make changes, then another "sacrifice" ride is going to be in order, and on and on, until you have everything set up the way it needs to be. Also, don't forget that the jets have one size thats different, and mix up which side takes the odd richer jet.
 
mopar1rules said:
on your '99 srx, the mag side gets the richer main.
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Thanks for the info. Big jet on the mag side is the way this sled is jetted, gives me a little more confidence that whoever set the sled up to begin with had a clue.

If I ever get my shocks back from Works ill be able to go for a few test blasts out in the field to make sure its close enough to trust on a ride when/if it ever snows here in Vermont :letitsnow
 
where in vermont? Brattleboro here. I have a 98 srx 700 that i just got cheap and am wanting to tear into it. Previous owner did nothing for upkeep at all. 4 inches here last night, keep on snowing.
 
tommey66 said:
where in vermont? Brattleboro here. I have a 98 srx 700 that i just got cheap and am wanting to tear into it. Previous owner did nothing for upkeep at all. 4 inches here last night, keep on snowing.
Click to expand...

I am in Springfield, I hear ya about the upkeep deal, I think the guy that owned the sled before me did not know what a grease gun was and had hit everything but the lottery :o| But its been a good project for the most part, the sleds not bad to work on and parts are out there.

My shocks just got back from Works and the reeds should be in tomorrow. Just gotta bolt the front suspension back on and hope for the best i guess. Good luck with yours, If you need something shoot me a PM, I have all the stock suspension that came with the sled, looks brand new to me.
 
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