2013 PRO 800 mid range miss/bog

gtwitch · May 8, 2016

My son's 2012 Pro 800 163 has had a minor bog in mid range 4900 to 6500 rpm and became serious day before yesterday and is now very repeatable! When you go slowly thru this rpm range, one cylinder drops and the other carries up to about 6500 where both now light up again and runs strong to 8200. Some thoughts here, first reeds, but that should effect all rpm and bad idle probably, Plugs look OK so don't think it is ignition and have changed out plugs, looking towards injectors?? and will check for air leaks at throttle body. Had someone suggest to look for chaffed injector wires possibly from rubbing from throttle cable?? Anyone seen any issues here? Just looking for someone else's suggestions here.

gtwitch in wyoming

Murph · May 8, 2016

If plugs look good and you swapped out with no change--check the plug caps for a carbon build up where they contact the spark plugs. The carbon can redirect the ignition pulse to ground-- the course of action is to spray contact cleaner up in the plug cap and use a pipe cleaner (or something similar) to clean it up.

The other thing to check is the ignition wire itself where it mates with the cap-- the wire strands erode inside the insulation-- remove cap, clip wire back 1/8" reinstall cap.

Both those issues could produce the running problems you are describing.

Murph · May 8, 2016

Another thing it could be is exhaust valves opening/ closing....

Do the bellows look good and hold pressure or is there a pinhole in one of them. What exhaust springs are you running? Stock orange or green/ white? What altitude? What psi are you getting out of a compression test on cylinders (since cylinder pressure opens valves)

Are the valves themselves clean or are they dirty/possibly sticking?

gtwitch · May 8, 2016

Great suggestions, more things to look at and I will! Thanks!

gtwitch in wyoming

Scott · May 8, 2016

Plug the exhaust valve drain tube.

It will make the bottom end run a little rough, but you'll find out if it cleans up the midrange issue.

I plugged mine with a small stick that I broke off a tree branch. It worked. It told me a lot.

Make sure it seals tight.

hamlin · May 8, 2016

I agree with the plug boots, I had a somewhat similar issue and thought my sled was fouling plugs which was weird because it never had before. Turned out my terminals in the boots were making poor contact, replaced the boots and no more problem. Sled had about 1000 miles then.

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2013 PRO 800 mid range miss/bog

gtwitch

Well-known member

Murph

Polaris Moderator/ Polaris Ambassador/ Klim Amb.

Murph

Polaris Moderator/ Polaris Ambassador/ Klim Amb.

gtwitch

Well-known member

Scott

Scott Stiegler

hamlin

Well-known member

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