SXR Limited Setup Rebuild Questions

chixwithtrix

chixwithtrix

Addicted
Location
Houston
My current setup is done for, hundreds of hours and I just got into racing this season. Looking to race in the women's limited class and I got some unfortunate news about my current Group K setup that the previous owner had done.

I talked to Group K and they poo pooed the idea of a limited boat (not surprising), but since it needs a rebuild I wanted to go limited since there isn't a stock women's novice class available.

I was hoping I'd be able to get the Group K cylinder re-sleeved, but they told me the ports would no longer match. So I'm left with a GK cylinder at the end of it's life. They recommended I start over with a new cylinder. I also need to replace the crank and head. So. I'm making this thread to get opinions.

I'll be going with an OEM Kawi crank
Have a Factory dry pipe
Should I buy a new cylinder or find a used one and get it sleeved for a little more bore, but stock porting?
Head...I guess I'll need to go girdled head with the heavy dry pipe. Thinking ADA unless someone has other input?
Carbs, currently have stock 38s, should I re-jet or get dual Mikuni 44s?

Thanks all, I'm new to working on jet ski engines so forgive my ignorance.
 
user_error

user_error

Location
seattle area, Wa
On the cylinder it depends on what you want too do with the ski. If you want to build a limited that will work well for a race here and there then i would recommend finding a standard bore cylinder, either new or used, and running it. If you want to build an all out competitive 2 stroke limited I would recommend finding a used cylinder and boring it to 84mm. the additional bore does increase the bottom end hit for starts and pulling out of the corners.

For a cylinder head id stay away from ADA and look more towards the kommander or TBM girdled heads. Make sure you run the .060 base gasket and get the proper .050 drop down domes for the head. Raising the ports on a limited with the thick .060 base gasket helps with top end speed quite a bit.

You can make the oem carbs work pretty well, but nothing really compares to a good set of novi-tec carbs. Either 46 or 48mm will work much better than oem carbs.

Lastly, when building race skis i've noticed that many people overbuild their ski and then cant ride them. Make sure you build something you are comfortable on. What i mean by that is when a guy spends tons of money building a 66 mph triple ski and isnt in good enough shape to ride it the guy will turn slower lap times. If the guy had a milder 60-62mph ski he would probably feel more comfortable and confident, allowing him to turn faster lap times.

Sometimes slowing down and getting really comfortable with a setup is better than an all-out balls to the wall setup.

Be sure to dial in your handling components in coordination with the added power as your riding style will change when you do the limited mods.
 
V

Vortex

Location
Southeast
I'm no expert but the previous post is spot on.

Limited class is being phased out in some sanctioning bodies. Pro watercross now calls it super stock. Basically mild 1100s. No strokers or high dollar carbs.

Since you have the dry pipe, maybe keep the internals all OEM, no need for a big bore, them add an ignition and a/M carbs, intake and reeds. The a/M carbs and manifolds are more tuner friendly

As was mentioned do not overbuild your race ski. Build your endurance on a stock (ish) ski until you can do 20 minute Moto's without slowing down much. 2 laps on an 1100 is like 20 minutes on a stock ski.
 
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V

Vortex

Location
Southeast
In other words don't blow all your money on go fast parts that compromise the reliability and endurance of your engine (unless your budget is not a concern). A nice stock ski will do 52-54mph and last a long time
 
chixwithtrix

chixwithtrix

Addicted
Location
Houston
I'm not looking to build it balls out, more on the reliable side than the fast side. I'm not looking to win, I'm too new right now, just be more competative than I am with a stock boat and be able to grow into it. The tiredness of my current motor has forced my hand to rebuild.

I'm leaning toward a stock cylinder bore for speed's sake, but a new OEM cylinder is more expensive than a used one bored out, obviously haha.

Heads are still a kind of a mystery for me, some require modification, some are just bolt on? That's why I was leaning towards the ADA because it required no other work. Unless I misunderstood posts in my research.

Thanks for the replies!
 
MTRHEAD

MTRHEAD

Location
MotorCity
Listen to user_error. He is the world champ! A 55-57 mph limited is fine for 99% of the riders. It's simple to get to 55. Also - stay with Kommander head if buying new or Kommander/TBM/Speedwerx for the domes. (All same squish design).
 
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V

Vortex

Location
Southeast
Cyl head is basically a bolt on (in general, I don't know exact sxr800 specifics) not counting the actual set up of the cylinder, crank, and domes. Girdled heads install differently than non girdled, you have threaded sleeves that replace your cylinder to case bolts. Install those wrench tight then you thread your head bolts into the sleeve and torque to spec. This ties the head to the cylinder base for added strength.

I would for sure take user errors advice on the thicker base gasket and drop down domes for more top end.
 
chixwithtrix

chixwithtrix

Addicted
Location
Houston
Ski engines are so damn different, I've rebuilt motorcycles and worked with car engines...multi-cylinder 2 strokes are new territory. I'll be doing some more research on the domes and such. Thanks for all the great info!
 
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