858 big bore dropping a cylinder?

Thanks. Much appreciated.

I have my 858 put back together with about 20 miles on it. 3/4 throttle and it does the same thing, cuts out, let off and hit it again, cuts out. I can't even slowly take it up to wide open. There must be a fix as there are quite a few sleds that are doing this. 2014 pro, 12.5 domes, 858, boondocker box, 1200' elevation, 50/50 av gas and premium. Previous owner said it ran great up on revy

Found this on snowest for your elevation.


Here is my fuel numbers running 91 NON ETH pump gas at 1200FT. I have 9 grams heel 5.6 mid and 3.5 tip on rooster weights. Total weight of 74.1 grams. Running a 150-340 (bright green) primary spring. Secondary is Team tied with a 140-200 spring (red/blue) and a 73-61 .46 helix. Gearing is at 19 top and 45 bottom. This setup is working very very good. I am hitting the rev limit every once in a while. I think i am going to add .5 gram more to the tip and see how it works. Snow is very light and it's cold here. Warm day in heavy snow i don't think it would need the extra weight. Hope this helps some of the lower elevation guys out.

EDIT** Clutches are very very cool with this setup also.


2500: 00 00 00 00 00 00
4000: 02 02 02 03 03 03
5000: 03 03 03 04 04 04
5500: 04 04 04 05 05 06
6000: 07 07 08 09 09 09
6500: 08 08 10 11 11 11
6750: 08 08 10 11 11 11
7000: 10 12 12 13 14 14
7250: 09 11 12 15 15 15
7500: 09 11 12 16 16 16
7750: 08 10 11 17 17 17
8000: 10 12 12 18 18 18
8500: 11 13 14 18 18 18




Sent from my iPhone using Tapatalk

Here's his updated info.

Did 120 miles yesterday and tuned most of the way. It is running very very good at these #'s. Rode 800-1500 feet. Below 1000 i was still hitting rev limiter with 74 grams in. Even a couple times above 1000. Gonna try add some more weight yet i guess. The more i drive this engine the more power it seems to make!! I still think these numbers are a little rich on the top end. Next ride i am going to pull a couple more numbers out from 7500 and up. Right now it's running 11.4-11.7 AFR above 7500. The rev limiter needs to be disabled with this engine below 2500 ft i think. It just revs so fast and high that it trips it a lot unless the engine is very loaded. A couple minor inssues that never really bothered me during the 120 mile ride yesterday. About 300 miles on it now.


2500: 00 00 00 00 00 00
4000: 03 03 03 03 03 03
5000: 04 04 04 04 04 04
5500: 04 04 04 04 04 04
6000: 10 10 10 10 10 10
6500: 10 10 10 11 11 11
6750: 08 08 10 13 13 13
7000: 10 12 12 13 13 14
7250: 09 11 12 13 14 14
7500: 09 11 12 14 14 14
7750: 08 10 11 13 13 13
8000: 10 12 12 16 15 15
8500: 11 13 14 17 17 17


Sent from my iPhone using Tapatalk

Any update? Get it fixed? I have a Carl's cycle doing the same thing but we don't have any snow to even try to figure it out now.

Well my testing ended with a total loss of the sled, burnt to the ground. Had a couple burp/backfires and poof, burst into flames.

shop quad said:

Well my testing ended with a total loss of the sled, burnt to the ground. Had a couple burp/backfires and poof, burst into flames.

Click to expand...

I hope you've got insurance?

Got insurance, just hope they cover the accessories that were on it

So did anyone find a solution? I can't help with testing as my sled is gone. I would like to know a fix so if it happens in the future with my sled or others I could lend a hand to make things run.

Too much secondary spring and helix. You are slipping in the primary at full throttle hitting the rev limiter. Lets see some pictures of your primary clutch faces.