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Anyone have a recommendation for 40mm Round slides
on a 800 with a RK Tek head?

I'm looking for mains, pilot, needle jet, and jet needle.
 

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I`m also interested in jetting info.     I`m thinking about switchinng carbs to roundslids 40`s. I think I will bore the carbs to 42. RKT head ,ported 800-01, and I`m going to dekker twinns.
 

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I have spent a fair amount of time dynoing with those carbs.  I hope to have a jetting kit available in the fall.  If all goes well and i don't loose another dyno, I should be able to wrap up alot of little thing s on the 800.  Some problems with the 40 rounds are: oil injection lever is to short on stock 800's, need new throttle lever assembly (entire throttle, cable, lever).  Jetting is slightly different than 700's.  When I dynoes back in may/June I could get everything to work for testing but want to make things look and function better for trail usage.  Since the pump lever is a different length I need to check oil/fuel ratio.  I will keep all posted as things progress.

Damon
 

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What I would love to try is 670 ho carbs, 44mm roundies.They could plug rite into the dpm.then I would put ufos on em.racer.ca uses 44mm on there 800 .40 seems small for the displacement of the800.
ay even solve the mid range temps on the rktech head
 

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Squish Band,

I tried carbs from 38mm to bored 44 (46mm) and the best was 40mm for overall even on a ported motor.  The jetting problems with the larger sizes did not outweigh the power gains.  Yes the bigger carbs make more power but for trail use they would be finnicky.  The 670HO uses a totally different dpm system and could not be easily transformed to fit the 800 electronics.  It had an enrichining circuit that is no longer being used.  

GLH
 

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Damon,

Did you wear out the dyno or did the 800 break it?

This new work schedule is kicking my butt. I have many days off but working 12's leaves lots to get done on those days. I have 7 days in a row off each month. If you need a hand let me know.

Later, Ron.
 

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Ron,

I broke it on our 600 improved engine.  She let go at 10,200 rpm.  what a sound it made.  The hub slipped on the crankshaft and destroyed the crank, hub, dyno,hoses, etc.  About $2000 worth of stuff.
Anyway I should have it back together in a couple weeks.  Thanks for the offer but UI don't need help yet??

Damon
 

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You should set up a cam from now on to catch those times on film for us sled heads LOL. Sorry for your pockets pain.
Caleb
 

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Let me tell you all this:  I work around and test compressors that can require over 50,000 HP.  They can move as much as 40,000lbs of gas per minute through 56" pipes.  I have taken sound readings as high as 131 db.  My tolerance for loud noises is quite high from my job.  When a tiny little 600 tripple went from 10,200 rpm to 0 in .002 seconds, well , lets just say I had a cold one after the hoses were done flapping around.  The new dyno will be here in a week or so.  Thank god because we got in a few new REV 800's and soon to recieve a 600HO.  Time to see the internal changes...

GLH
 

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Hey GLHRACING,


I am replacing the pistons in a 98 670.. thinking about the ones for the 739cc..Have accuried 44 round for those pistons..have no idea, one how this would work and what the jetting should..Any suggestions would be great..Thanks

Bill
 

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Sound like he wants to big bore the 670 to740 and put 44's on it. If that's the case, let me know I did one last year, and can get you started.
 

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Wiseco sleeves and pistons. Install at 5 to 7 thou. clearance (depending on your warm up style.) Re-port to accomidate larger sleeve. Open up combustion chamber to match bore. 14:1 compression and .065 squish, if you can run premium all the time. Cut rotary valve to 150-80. Billet RV cover. Gut air box and bore those 44's to 46. BB-0 tube, 7EG06 neddle. 50 pilots. Mains depend on single or twin pipes. Easily capable of 100 ft-lbs and 150 hp. Your next issue is traction.
 

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Krusty,

You need to stop reminding me of those wonderful Rotary's.  I am tuning them out now. Series III, Series III, Series III...

OK, now I am alright!!

We run a 760 BB in one of our "440 mxzx"
Hill climb sleds.  That thing pulls 21 gr pins all day long on a hill.  I wish the new 800's could come close.

GLH
 

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Sorry about that GLH. The last good motor Rotax made was the 670. But you already know that. Is the 760 based on the 440 bottom or a 670?
 

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Krusty,

The 760 is based on the 440 motor.  It is an arm pulling machine.  156 [email protected] but torque comes on hard at 6000rpm.

Series III, Series III, Series III.  It is better, It is better, it is better...

GLH
 
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