88 Tundra hard starting, backfiring

Technical discussion related to engine performance, clutching, setup, and other snowmachine modifications.

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brasebear
Posts: 4
Joined: Sat Mar 27, 2004 6:40 am
Location: Fairbanks, AK

88 Tundra hard starting, backfiring

#1 Post by brasebear » Sun Feb 04, 2007 8:42 am

Ran pretty good (slightly rough/a bit low on power) all last year. In spring filled tank + StaBil, fogged, etc (summerized as usual). This fall a little hard to start, ran OK for day or two in Nov. This weekend went to fire it up and no dice. Plug looked ok and was dishing out blue spark. It'll catch and turn over 6-10 times every 5 pulls or so, then pops 2-3 times, then big back fire. Found crack in the rubber tube from airbox to carb which I'm going to replace today.

Any ideas on what/where else to start to smooth this out?

Thanks, Mike



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Alaskan Polar Bear
Posts: 209
Joined: Fri Jan 16, 2004 7:49 pm
Location: North Pole Alaska
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sick tundra

#2 Post by Alaskan Polar Bear » Sun Feb 04, 2007 1:10 pm

Hey Mike
Tony Martin here. (488 1330)
sounds like your sled has a simple problem gonna take a bit to figure it out though
pull the carb off and run your finger accross the piston side/skirt and feel how rough it is.
if it is pretty rough , and it doesn't take much , then you need to hone the cylinder and replace the piston/
I suspect that the split carb boot has been letting snow in and has scored the piston ,
checking the compression won't help
let me know what you find
Tony


No track and engine? what's the point?
2006 Polaris 755 RMK 159
2006 Polaris 755 RMK 151
2003 Polaris 550 super sport 121
2002 Polaris 700 RMK 144
1998 Polaris XLT Special 600 121
1976 Polaris TXL 340 Liquid
1972 / 74 Skiroule 300 RTX
and a few more

brasebear
Posts: 4
Joined: Sat Mar 27, 2004 6:40 am
Location: Fairbanks, AK

Figured it out

#3 Post by brasebear » Tue Feb 13, 2007 7:02 pm

Hey Tony,

Thanks for the reply. Here's what I found/did:

Found exhaust had been blown off the back of the engine from the backfiring -- reattached/sprung

Drained carb (looked like baaaaad ice tea with 'stuff' in it)

Drained all fuel from tank with suction pump + all lines

Removed carb and blew 1/2 can of carb/choke cleaner at the whole shebang

Replaced airbox > carb rubber tube with a new one (it was totally torn in 1/2)

Filled tank with fresh fuel

Started on the 2nd pull, and purrs like it never has before. Amazing what stale gas plus gurry in the carb can do. Although this was quite simple/quick, I was pretty leery of pulling the carb off, for fear of hosing something else up. All in all pretty easy job with great results.

Mike



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