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Discussion Starter · #1 ·
I have put a 04" 900 top end on my 01'ZR 800 with an 03' cdi with 53 degree helix, only 72 gram weights and a RKtech head set up for 0-3000' and 90 octane fuel.

Question is, what clutch weights should I be running. I have a set of 76 grams weights I was going to try next and a set of 82 grams.

With the 72's, I am killing five or six well set up F7's (03' to 05's) out of the hole all the way up.

RPM's are topping out at 7700-7800, I know that heavier weigths will bring the R's down into the power, but will I loose anything.

I didn't expect it to run as well as it has with the 72 gram weights, but if there is more, i want it.

Thanks, Joe
 

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Well if you bring the PRM down to 7200-7300. You will be much happier. Try a 63-54 helix with 76 gram weight....Maybe even heaver weight.
But what ever you do. Bring the rpm down and HANG ON!!!!!!!!!!!!!!
 

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The 76g's should get you close. You need to see 72-7300rpm out of the hole climbing to no more than 7500 on long pulls-providing your running the stock pipe. If the tach hasn't been calibrated keep in mind that most come from Cat reading 100-200 high. I think the 82's will be too much. :div20:
 

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Sorry to but in...
What power valves are you useing?
Are they 900 or 800's?
I have a 900 topend that my buddy wants to use but I don't know if the power valves will work.
Hope u can let me know what you are runnin'
 

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Discussion Starter · #6 ·
I had the carbs set up to 900 specs with a different needle to handle a leasn midrange condition on the 03' CDI mapping, I also found some 900 poervalves, but you could easily file yours down to match the new bore. I also have the stock pipe with a PPP Can. Kelsey at RKtek told me only one or two cans actually made power for this 900. I was thinking the 76's would be close, i found a set new on Ebay (d&d) for $20.00. Oh yeah, I also changed the gearing to 26/41 I think, stock for an 03 900.

If it goes faster, that would be coooool :smiley-faces7:
 

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Discussion Starter · #8 ·
What helix are you 900 guys running at low altitude? I am running a straight 53 Degree and it pulls hard, I have a few multi angle helixs but heard you loose backshift with them.

Any one have a good set-up to share, I won't tell anyone, I PROMISE!!!!
 
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