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Discussion Starter #1
I recently became a first time owner of two Indy 650 triple sleds. Both are vintage '88 & '90 with the '90 in the worst shape in terms of the body. Apart from cosmetic work and a couple new parts (water pumps are unbelievably expensive!!!) the engines sound strong and don't show significant signs of wear. The '90 PTO side piston shows slight scoring on one side of the skirt from the bottom up to the rings, I am a little concerned about that. The '88 has about 160 hrs on a new top end including some "fancy" Wiesco pistons.

Getting to the point, I have since heard that this triple is suseptable to overheating the center cylinder. I would like to hear any words of wisdom about how to treat these engines. What should I look/listen for? Should cylinder head temp sensors be installed? Before a take them out this year are there things I should look for? oil injection settings? Anything?

These being the first Polaris product I have ever owned I'd rather not make any stupid mistakes that could be avoided. Thanks for your input, I look forward to your replies.
 

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I have a 91 rxl 650 and i havnet' really heard too many negative things from the folks I've asked. I did hear about some problems wiht the cranks in the XLT triples but I don't know if it applies to the 650. I burned the top end in my sled The piston on the clutch side burned up and debris got into the center cylinder and scratched it up pretty good. But my sled has almost 9000 miles on it so I can't really complain about it. i didn't put too many of those on it but that's a helluva lot if that's problem engine.
 

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I have a 95 XLT Special. I know that run the same jet size in every cylinder. Most people dont know, but older triples, and some of the new ones run a different size jets in each cylinder. Check a manuel and find out what size jets go where and make sure the ones you are running are there. If everything is stock, (pipes, clutch) you should be able to use the two little score marks on the pump and the arm of the pump. line 'em up. If you are piped, it needs to be ran a little bit richer, about 1 to 2 mm between the stock notches. I dont have a temp gage, just a dummy light, and by the time a dummy light comes on, its usually too late. I have always wanted a triple temp sense, one for each cylinder, and tihnk its a safe investment, but have never gotten around to it. Scoring on the skirt is deffinately a bad thing. If its not deep, I woudnt worry about it. Its only a real bad thing if its effecting your cyl sleeve. If there are scratches on your cyl sleeve that arent too deep you can polish them out without going to a different piston size, but anything deeper than the thickness of construction paper should be replaced. if you though water pumps were costly, wait until you have one of these babies installed.....Hope this helps!
 

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VINTAGE? U CALL THAT VINTAGE>> THATS BLOODY NEW!.... below 1980 is vintage, bogie assemblies, and leaf spring suspensions... thats VINTAGE... what ya got there is new

Duct tape much like the force... it has a light side, a dark side.... and it holds the world together!
 

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Watch the plugs. If the middle cylider runs a little lean start to run a colder plug in it. And try not to over rev the engine.
 

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Discussion Starter #6
Thank you to all who have responded. I am especially interested in the multiple jetting issue. If this is indeed true for my engines then I've got to check it out. In the process of going through both engines I removed the carbs to clean them. At the time I paid no special attention as to which cylinder they came from or went back to. With the short grass runs I have been doing to check things out I have found the center cylinder fouling, changed out the plug twice but still get rough operation. Very "Doggie" in the low end. I have the pilot neddle set to about 7/8 turn, the main neddle is clipped at the second from the bottom setting (rich).

Thanks again
 

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I dont recall a pilot needle adjustment. Air screw and idle screw, and main needle clip are the only things you can adjust i think, if im wrong what types of carbs are you running, give me the type of carb and number and i will send you my documentation on them, it helped me. When you fould the center plug...is it oil, gas, water??? HOPE ITS NOT WATER. Could just be a 2 dollar jet. Get back to me with this because this is exactly what my sled was doing, and i put $160 into it before i bought $30 dollars of all new jets : ie. pilots, and main. i think i can help you if you can tell me whats building up on yuor plugs.

Need some darn snow people.
 

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Ill keep it short and sweet. The old triples were notorious for scorching the middle cylinder, but with synthetic oil and avoidance of lean carb conditions it will suit fine.
 

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Dial-a-jet and EGT gauges.
 

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I recently got a 89 indy 650 also. Center bearings in lower end were ceased. But got a good lower end and been blasting around on it. Maybe I could get some help from one of you all here. All is stock, except .020 over pistons, Has egt guages. what should be the temps above idle? book has around 250 at idle. what about mid and high range. I've never messed with these carbs and any help on adjusments and what to adjust would be appreciated. Thanks for any input
 

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I have triple pipes. The probe should be mounted 6"-8" from the exhaust flange. Test and adjust low throttle first - e-clip postiton for this. The EGT rtemps should be:

1/4 throttle - 900-1000 Degrees
1/2 Throttle - 1100-1150 Degrees
3/4 Throttle - 1200 - 1250 Degrees
Full Throttle - 1300-1350 Degrees

I'd keep her on the lower end of this map to advoid meltdown. And use fresh 92 octane fuel to keep her running cool.
 

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thanks RXLRIDER. I can only get 90 octane fuel out here in alaska. I'll have to hunt around for some. I don't have pipes, but regular stock manifold and probes are about 2-3 in from flange. These temps are in range, slightly on higher side though, The e clip is on the top groove though I'd move to the center spot, and try today. If I'm correct in thinking this shold richen it up and bring to lower side of temps. Thanks a bunch
 

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Discussion Starter #13
Thanks Sky, you are right about the pilot jet, it has no adjustment, I was refering to the Air Screw as you noted. I went through all 3 carbs including the pilot jets to make sure they were clean. Also, I'm 99% sure that all 3 carbs are set-up with the same main jets/needles. I ran the engine a couple of times and swaped the center and PTO plugs from one cyl to the other. Each time I inspected the plugs the center was "wet" with fuel and the PTO was nice and dry. The engine seems to run "choppy", it pops intermittently like the center cly may be firing erractically. My next move was to replace all 3 plugs and try it again. I also am starting to suspect and electrical issue with the center plug wire or coil. Since the coil is buried below the carbs it's difficult to do a visual for loose wires or arcing. The previous owner claims to have completed the Top End rebuild less than 160 miles prior. It is possible that he missed a ground wire or didn't properly plug something in.
 

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This may be minor, but dod you check spark in the center plug? All 3 should be sparking at the same time.
 
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