HUGE Start Up Backfire | Ski-Doo Snowmobiles Forum

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FormulaZ583nb F My 05 800HO PTEK has just started doing this in the last week to ten days. When its cold (after sitting overnight or for a couple of days) when I start it (with the electric start) it will start up fine with the choke on - but when I take the choke off, after a couple of seconds, it will stall itself out. Then when I restart it the second time it will make this huge, huge, huge backfire - unmatched by any 12 gauge I have ever heard. After the backfire it seems to run OK. When it did it tonight - the idle hand stayed up on 1500 RPM or so and the electric start did not have enough juice to crank the motor, so I had to get it going with the pull cord, even though the battery is fine. After it started I shut it off a couple of times and the battery would then start it right up????? The sled now has 2500km on it and everything is stock - and the 07 ECM Update has not been done (as of yet). I run blue marble oil and always high test/supreme gas with isopropol alcohol as needed. Any ideas what is going on here - I checked the compression before my last ride and it was about 137 / 139. I hauled the plugs out tonight and they were oily but both tips seemed to be a little white, but just the tips. I have been battling with the oil pump adjustment - trying to get it to around 40:1 and its getting closer with each adjustment. I think I have read so many horror stories about these 05/06 800's that I am just waiting for it to blow up. Any help would be appreciated. #1 · Jan 31, 2008 (Edited by Moderator) My 05 800HO PTEK has just started doing this in the last week to ten days. When its cold (after sitting overnight or for a couple of days) when I start it (with the electric start) it will start up fine with the choke on - but when I take the choke off, after a couple of seconds, it will stall itself out. Then when I restart it the second time it will make this huge, huge, huge backfire - unmatched by any 12 gauge I have ever heard. After the backfire it seems to run OK. When it did it tonight - the idle hand stayed up on 1500 RPM or so and the electric start did not have enough juice to crank the motor, so I had to get it going with the pull cord, even though the battery is fine. After it started I shut it off a couple of times and the battery would then start it right up????? The sled now has 2500km on it and everything is stock - and the 07 ECM Update has not been done (as of yet). I run blue marble oil and always high test/supreme gas with isopropol alcohol as needed. Any ideas what is going on here - I checked the compression before my last ride and it was about 137 / 139. I hauled the plugs out tonight and they were oily but both tips seemed to be a little white, but just the tips. I have been battling with the oil pump adjustment - trying to get it to around 40:1 and its getting closer with each adjustment. I think I have read so many horror stories about these 05/06 800's that I am just waiting for it to blow up. Any help would be appreciated. See less See more Sort by Oldest first Oldest first Newest first Most reactions #2 · Jan 31, 2008 Anyone having the same experience???? #3 · Feb 1, 2008 I just started it again tonight to recheck the compression and it did it again - huge backfire after it stalls out and is restarted. The electric start won't turn the engine over on the second try to start it, but i can roll the clutch and turn the engine so it is not seizing. The battery must be getting weak but that is another story. Anyway, I restarted via the pull chord and let it run for 30 seconds and then pulled the plugs to check the compression and they were soaked with gas - almost dripping wet. The compression after 30s was 140/141 PTO side and 143/144 MAG side. I put the plugs back in and then let the sled warm right up and took them out and checked the compression again and it was 135 PTO & 135 MAG. Rings may be starting to get bad, especially on the MAG side? As for the explosion that happens when it stalls (and it never did that before) and is restarted - I really think that I may blow a seal somewhere or do some damage if it is not already done? Is it possible that it could damage something through backfiring? Any help or advise would be greatly appreciated. #4 · Feb 1, 2008 sounds like your running it too long with the choke and flooding it... Compression is fine, dont worry about that. Yes, backfires are hard on crankseals. its an 05 ptek so it should have the retainers already #5 · Feb 1, 2008

06MXZXRenegade800 said: sounds like your running it too long with the choke and flooding it... Click to expand...

I agree that he's getting to much gas. My question is, he said in his original post that he's only keeping the choke on for a few seconds, and if it's only a "few seconds" it shouldn't load up and kill it. I wonder if something is hanging in the choke making it get more fuel even after he switches the choke off. 0 Reply #6 · Feb 1, 2008 whatever it is make sure its fixed soon ,my buddies 800 sdi did it last winter before it blew up #7 · Feb 1, 2008 I am stumped on it - definately not leaving the choke on too long, only a second or 2 and then I flip it back. It only started doing it last week? To me it almost seems like a timing issue or something like that. I will have a look at the choke and see if something is binding or sticking but I have my doubts that is what is causing it. Anyone else seen this before?????? #8 · Feb 1, 2008 For the sled to backfire like you describe the exhaust has to be loaded up with fuel. You may have a carb, needle/float that is bad or out of adjustment. This allows the engine to load up with gas while it sits for periods of time. You crank it and the fuel is pushed into the exhaust. It's all ready rich so it stalls. You try to restart and boom. #10 · Feb 1, 2008 I thought about that as well, but if this were the case then why wouldn't it explode when it first starts up. The backfire happens when the sled runs for a couple of seconds and stalls out due to flooding. Then when I start it again is when it backfires. If the gas was present at the begining it should backfire right away shouldn't it? In the next week I plan to up the pilots, drop the mains a size and get the 07 updated needles and have the ECM reflashed. I am also installing a set of Boyesen Reeds as preventative maintenance. So, while all of this is being done I will have the carbs looked at for the second time this year to see if there is anything wrong in there that would cause this to happen. Anyone else have a suggestion??? 0 Reply #9 · Feb 1, 2008 After a big backfire or a couple of them you should check your reed petals. They either tend to crack or break the edges off,whether they are stock or aftermarket. I too seem to think it is something in the carb jets. Maybe a little dirty or gummed up. Maybe a can of sea foam would clean it out and see what it does after that. Hope my little bit of info helps ya! #11 · Feb 2, 2008 I have a new set of Boyesen Rage Cage's to install - just waiting on the jets, pilots and updated 07 needles to arrive and I will go ahead and put those in. Probably clean the carbs again then as well. I just put a half can of sea-foam in the tank and I will probably change the plugs tomorrow before I try and start it. I don't think the plugs would cause this sort of thing to happen but for the cost I will give it a try for sure. Thanks for the suggestions - keep em comming. 0 Reply #12 · Feb 2, 2008 (Edited by Moderator) I agree on the fuel thought. Get the sled on the cement lift the front end up as high as possible and drop it down. Repeat process a few times, then check it out. I have unstruck numerous floats this way in order to get them home and repaired properly. If playing basketball with it fails, try the Seafoam it's great stuff. #13 · Feb 2, 2008 (Edited by Moderator) Try putting in a new set of plugs, gapped to spec (can't recal stock setting). On the first press of the button don't use choke, when it stops sputtering, then choke. Pull off the choke when it starts and feather as needed until it runs on it's own. This assumes there are no leaks in your Y pipe or the gasket......The flooding won't cause ignition in the exhaust, without extra air being introduced.. You might want to check the notorious carb boots too! They could be torn. Cheers! #14 · Feb 2, 2008 TTT - anyone else have any advise? 0 Reply #15 · Feb 22, 2008 Kind of curious myself here....last night mine shut down after putting it in reverse. sputtered and shut down. pulled the cord and blew off a 10 gauge boom. Nothing now. Put a new relay in and got it running in the garage. went to pull it out and it died. *%@ ! I thought I was home free. So i'm down to thinking it was the stator or the ecm. I can pull on it and nothing, then suddenly i get it to sputter for a few seconds, but sooner or later the backfire comes....man is it loud. I was thinking maybe the ecm was damaged and putting me out of time. I've checked every wire through the schematic. Running out of ideas. so much for the 600 mile loop this weekend :-( Let us know what your dealer finds. Insert Quotes Post Reply

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