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Discussion Starter #1
I went for a ride with my son today in upstate NY, near Ithaca. It was quite warm, around upper 40's. No problem when I first started out, although uphill it was bogging from 4000-5000 rpm. When I got it up to over 5500 rpm it ran fine. The bogging got noticeably worse further into the ride. After about 1 1/4 hrs, it was all I could do to get uphill. The engine is completely stock, never had any problems yet, 5700 miles. I always use premium fuel. I did put an Xtra-10 suspension under it last year, but I have used it a lot this year and no problems until today. Could the warm temps have anything to do with it? My son was riding a 440 fan cooled super sport, and he had no problems the entire day.
 

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I had a similar problem, it was the pilot jets in mine. Check out this link :

http://www.snowmobilefanatics.com/snofan/topic.asp?TOPIC_ID=5253
 

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At the risk of insulting anyone, did you check the plugs? Could just be fouled plugs.
Dan in NH
 

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I read on the fourms about someone who had a clogged fuel filter. There wasn't enough gas getting to the carbs causing a bog. Also, your belt could be bad. If it were worn down, it would be like the snowmobile is starting in second gear...
 

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If you have 5700 miles and have never rebuilt it thats the problem right there. Check the compression. Once it starts getting low there will be less power and if left alone long enough the sled eventually will barely drag itself around.
 

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Discussion Starter #6
Brand new belt this year. I changed the plugs in the middle of the ride, didn't make any difference. As far as a rebuild, I have heard of the Fugi 488 going a lot of miles before a rebuild. I am in the process of taking the carbs off now to check the jets, but I will check the fuel filter also.
 

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And 5700 miles isn't a lot of miles[?]

Warm temps, ie rich jetting, would cause excessive smoke, wet plugs and a deeper exhaust tone...did you have any of these?

I still bet its got poor compression
 

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Discussion Starter #8
I would say 5700 is a fair amount of miles, but from other posts, riders of the Indy 500 are saying that they have gotten over 10K before rebuilding. The engine ran sluggish when bogging, but when it hit the powerband around 6000 rpms, it caught fire and ran fine. Plugs were a little dark, so I assume the sled is running rich, which is pretty much the way they are set up from the factory. Exhaust sounded normal, again, only bogged at the lower rpms, ran great above 6000.
 

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yep, the beginning signs of low compression. At low rpms it will be most noticeable. Seriously do a compression check before going any further. It's a 30 second test that tells you where to start troubleshooting.
 

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A compression check sure couldn't hurt & it only takes a couple minutes. I had the shop check my compression on my '97 Indy 500 at 10,000 miles after having them work over my clutches and it was still new compression... the shop guy was amazed. Unfortunately I melted her down 200 miles later because of a cracked carb boot.

Did you pull your carbs off and blow out your pilot jets?
 

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my opinion is the same lack of compression but i will add a side note here it sounds like a stuck ring from not fogging your engine down last spring. compression test will confirm this.[:)]
 

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Discussion Starter #12
Ok, I did the compression test. 125 lbs of pressure each cylinder, very even. I have pulled the carbs off and and am giving them a thorough cleaning. I plan to put new carb boots on when I am finished. While I have it apart, should I have the crankcase pressure tested? I am wondering if there is a leak letting air in. However, I can't see anything around the clutch side, which is where this usually happens, right? If I had water in the gas it would have run poorly throughout the rpm range, yes
 

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I was surprised to hear people say that your engine should have been rebuilt by 5700 miles!

My '89 Indy 500 has well over 15,000 miles on it... it popped a piston at 14,500, but that was due to bad fuel. One piston (not even oversize) and it's still running strong!
 

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Ray if it is a 488 fan cooled and you were running it in close to 50 degree temp. I would say the warm temp was your problem. The fan cooled Trail Indy runs best in the cold weather. It's probably a combo of the motor getting hot and the clutches getting hot. Plus you may want to check your secondary clutch and make sure the plastic buttons are not wore out. Riley
 

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Discussion Starter #15
The fan cooled sled riding with me experienced no problems that day. My liquid cooled sled was bogging. Just finished taking the carbs apart and cleaning them. There really wasn't anything in them that would have messed them up. I am running 300 main jets, and I am wondering if I should go to 290?
 

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start out by raising the needle clip one, that'll have the most effect on midrange. If you run WFO you may notice that the motor will load up and begin to bog (when it's warm out)...thats when you need to lean the mains out.
 

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Rocket Ray - you say you're runnin 300's on the Indy 500. Believe stock is 350 (or it is on my 98 Indy 500) so you're getting pretty lean at 290. But that's really a side issue as the main jet doesn't come into play until higher throttle. So should not affect your low end problem.

Essentially the pilot jet restricts flow up to 1/4 throttle, then the neddle jet/jet needle assembly kicks in up to 3/4 throttle, then the main jet from there on.

I'm having intermittent bogging problems on my Indy 500 at the moment, what I first thought was my primary sticking I'm now thinking is a stuck float. Need to take the carbs off and have a good look. But could be your pilot jet is plugged, as this would affect low end but not high end. Let us know if you get it figured out...
 

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Discussion Starter #18
Looked at the floats when I had the carbs apart, they were fine. I checked the pilot jets very carefully, took them out, cleaned where they fit into; they were clean, no junk. I don't believe I have a crankcase leak, it starts easily. I am going to change the fuel filter, carb boots, fuel pump and fuel lines. After that, clutches and CDI are next. Thanks for your ideas, and keep them coming. I'll let you know how I make out, ordering parts tonight. The snow around here is mostly gone after today, but if I can get it running again, I will go up north.
 
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