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XT350 Experts.... Help?

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I am in the process of rebuilding my 93 XT350 and am looking for more performance. I have also noticed many people mentioning a 17hp version capable of being increased to 30hp, what years are 17hp and what does it take to open them up? Does anyone know of performance pistons?

I currently have: a cobra exhaust, bored .5mm over piston, uni oil filter and moose bars.

I plan to: install a 17 tooth sprocket and heavier weight oil in the forks.

Any help or recommended mods would be GREATLY appreciated.

Thanks

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Is the 350 really a 348cc? Sounds alot like the motor in the Warrior quad, alos good for about 17-20 HP. The only way to practically double it with a two valve head is going to be a big bore kit and proably stroking it. I've seen Warrior motors punched out to 490cc by Mickey Dunlap at Four Stroke Tech but it's serious money, approx. $2500 for motor work alone. There are also smaller kits with less power that are much more reasonable.

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This is a great bike. Go to www.bikez.com to see the horsepower specs for each year of the XT350. I can't remember which year had the reduced HP but remember seeing it on this site. I still have an 87 XT350 with only 5,800 miles on it. This year had 27 hp and the motor is bulletproof. I have a Supertrapp exhaust on it and the gearing is way down. It is a great woods bike. These two changes make a big difference. Top speed is only 70 now. Now that I have the KLX400, I don't ride this bike anymore. I have a ton of spare parts. PM me if you're interested.

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I also have a ton of parts and a whole bike if anybody needs anything.

RAMBO, I have not forgotten about the speedo drive. I just have not had time to pull all the crap out to get to the bike.

I will PM you when I do. Maybe this weekend.

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Thanks for the responses:

I am not really looking to make this an all performance machine. The older model XT's are rated at 27hp (85-90) and the newer ones, like mine, are rated at 17hp.

The only real 'mods' I am planning are to install a 10.5:1 compression piston and airbox inserts, as well as, cmotts power now.

In short, I know any increase will be nice and I hope to make mine perform a bit better than stock 85-90. Also, anyone know anything about jetting one of these?

If you have any advice, or can offer technical assistance please pm me.

Thanks

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Hey everyone. I know its been a while since this thread died, but I'm currently looking into getting an XT350, and this thread caught my interest.

I checked out the specs for the XT350 on Bikez.com, and found that the 17 hp XT350s had a "Reduced Effect" notation after them. It appears that these "reduced effect" versions were made in the early years, '86 - '90, along with the 27 hp versions. How would someone tell the difference when looking at a used bike? Why would Yamaha offer a version of the same motorcycle with LESS power?!

After 1990, the xt350s apparently only came in a 17hp version. That is a big drop in horsepower!! Are the two engines the same, and can whatever limits the 17hp engine be removed/altered to bring it up to 27hp?

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First of all, where the hell is everyone reading these HP figures from. One thing to remember, the bikes HP is probably 27 at the CS sprocket, and usually there is a 33% drop at the rear tire, where it is obviously where the 17hp figure is coming from. Another thing, these are NOT 2 valve motors, they have 4 valves. Don't worry about HP concerns unless you live in CA where they "might" have some smog canister mounted which "might" account for a 1-2 HP drop.

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I too am an Alaskan. I race locally(mx season is over). I have lots of experience with jetting. I owned a XT600 for 9 years. I have lots of jets for my WR450F, Mikuni and Kehin carburator jets are sized differently though. I am down in the Soldotna area. PM me.

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Everything I have read on the internet shows in 1990-1994 they had 17hp then went back up to 27hp in 95+ I have a 1992 and this is upsetting, somebody, what could change 10hp? (jetting and exhaust??)

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Everything I have read on the internet shows in 1990-1994 they had 17hp then went back up to 27hp in 95+ I have a 1992 and this is upsetting, somebody, what could change 10hp? (jetting and exhaust??)

Probably the method in which HP was measured as Yamaha hasn't updated that 350 in a very long time. I owned a '85 and '87 XT350 and a '89 XT600 and all were great bikes.

Neville1 wrote,

One thing to remember, the bikes HP is probably 27 at the CS sprocket, and usually there is a 33% drop at the rear tire, where it is obviously where the 17hp figure is coming from.

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i belive the restriction was put in place to make a already bulletproof engine even more bullet proof. this is done by a throttle restrictor and a restricted carby the throttle is easy all u doe is remove the little screw that it has holding it. or if it is one of the later ones u will need to find a new throttle asembly. enjoy. :cry:

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