88 Indy 650- runs great on stand, loses power after 4rpm on ground - Snowmobile Forum: Your #1 Snowmobile Forum

XCR KDX NJ · 10-07-2009, 04:06 PM

I recently got an 88 indy 650. Cleaned carbs, ran new fuel lines, ran great. I never took it for a spin in the grass because of other projects going on. I decided to take it for a spin in the grass and I warmed it up on its stand, starting, idling great at 1900 rpm, air screws 1.0 turn out, all carbs synced. The track spins nicely. When it accelerates past 4000rpm it feels like its choking but doesnt bog and stall, just feels cut off from power. The clutch engages right off the bat, I never had it apart or took one apart, I saw that it moved well when it engages, there's a gold spring. When I take it off the stand and accelerate, it has a short burst and moves 2 feet tops, and then dies of power. The clutch engages, and the belt just smokes up a storm. Even with my weight off the sled it does the same. Could jetting be incorrect ? It feels like all carbs are working well. Any suggestions? Thanks

Polaris87 · 10-07-2009, 05:53 PM

somethings wrong in the clutches. Check the spring in the primary. It could be broke. I know gold is stock on the 600 XLT's and 500 Indy. Not sure about the 650. What RPM does the clutch grab the belt? 4000 RPM? If I were you I would take the clutch cover off. 6 bolts. And check the spring. If its engaging at 1500 or something lower than 4000 its probably the spring. But take the cover off and have a look. There is an X on the cover and a X on the Spider. Make sure u match the X's up when you put the cover back on. Also look at what weights are in it. They are marked on the side. Write it down and post it on here. Also check to make sure there are no flat spots on the rollers and that they spin freely. Also check the weights for flat spots or grooves cut in them.

If the spring is ok and its engaging around 4000. It's in your secondary. Could be a broken spring in there or other problems. Take the primary apart first. Thats the easiest one to do.

**RJ Gleason** · 10-07-2009, 06:08 PM

Start by checking the plugs are all firing.
If it engages the clutch properly on the stand, it should still do so under load.

Polaris87 · 10-07-2009, 09:00 PM

I had a sled that would turn up 8000 on a stand. Put it on the ground and it would go 6 feet and bog out and hardly pull itself....

XCR KDX NJ · 10-29-2009, 01:44 PM

I started the sled while its on the stand, it idles strong, all three cylinders are firing. The first time I punch the gas, to engage the clutches and to rev the motor up, I glanced at the tach and the sled hit 7 or 8 thousand, sounding outstanding, like a 3 cyl two stroke should sound, beautiful. Keeping it in that high rpm range for a few seconds, I noticed the front clutch engaged, sliding nicely towards the motor, and the rear clutch, spreading apart as the rpm was high. Once I let the rpm's drop to idle, the clutches back to they're sitting positions, and hitting the brake, the track to a stop, it idled great no stalling. NOW, doing the same thing again, same situation except this is the Second time I am opening up the throttle since starting the sled, engaging the clutches, making the track spin, bringing the rpm to a high rev, the sled now does NOT hit 7 or 8, it now goes no more than 5 thousand rpm, clutches engaging, track spinning, and the motor feeling like its gutless. While reving the motor in this range, trying to keep the tach high, 5 is as high as it will reach, and when pushing more throttle to WOT, the motor not reving any higher, but but sounding like its letting out a bellow, a deeper sounding rev like it is unable to get into its power range.

I changed the plugs to RN 2C which it says under the hood, and they all have perfect color. The clutches move like they should, I even put a new Max 3 belt on there. What could be the problem? It hits perfect the first time going WOT, - letting the motor drop its rpms to idle, and the second time trying to go WOT it will not rev out like it just did.

THANKS FOR YOUR REPLIES

**RJ Gleason** · 10-29-2009, 04:11 PM

When you checked the plugs, was any of them wet?

XCR KDX NJ · 10-29-2009, 04:22 PM

I checked the plugs after I ran it just now, they all were the same color, light tint brown, with very light coat of oil showing. My xcr blew a crank, so I advanced the oil injection a slight bit on all my sleds. I just inspected the fuel lines and took apart the fuel pump, which was clean as a whistle, and put a new fuel filter on. Same result, once started and warmed up idling, punch the gas to WOT and she screams. Once it goes back to idle, and punched to WOT again, only revs to 4-5 rpm at most. I cleaned the carbs a couple months back. It seems to run great when the first WOT is applied.

One thing I did notice:
The airbox is off, so I have a clear view of everything. When she is running and I punch the gas, I notice the center carb sometimes shoots out a very light mist of what seems to be gas. That cylinder is running however.

I tried to upload a 10 sec video clip of the motor when it runs to show the sound of what happens, but it is an "avi" clip and this site doesnt allow it to be uploaded.

mrholmquist · 10-29-2009, 04:32 PM

leave the rear jacked off the ground. start the engine and slowly raise the rpm until the clutch just starts to engage. That is how you find the engagement RPM. As stated above if the engagement RPM is below 4000 you have a clutch issue. Most probably a broken or weak primary clutch spring just like Polaris87 said.

In your second post the conditions sound like there is not enough fuel getting to the engine as you mention it ran good first then not good. If the fuel supply was restricted and the carb bowls were full to start with it may have ran ok for a bit. Then as the fuel was used up in the bowls start to run bad. You mentioned new fuel lines I assume you replaced the fuel filter (make sure you put it in the correct way around) but you could also check the screen on the end of the fuel line inside the fuel tank.

Also check to see that the choke cables are adjusted correctly and all three plungers are seating properly when the choke lever is down

XCR KDX NJ · 11-05-2009, 01:47 PM

I have done what you said. The engine hits 4000 rpm and then the clutch engages. I took off the primary clutch and it seems to work properly. There are no flat spots on rollers and each weight moves freely. The main gold spring is not broken or snapped. The secondary clutch was just removed and when I am holding it, it has no knocks or noises from the inside. It rotates the opposite way from each side and the springs inside are strong. I did not take it apart. Could there be something in there broken even though it feels strong and in working order ?

The motor gets fuel just fine, I see all lines flow when its running.
Also, once the track starts moving while its on the stand, its wont stop spinning even at idle, unless I apply the brake. After its been sitting, first time starting the track does not move. Once I get it out of idle and let the clutches engage, the track moves and keeps moving; unless I hit the brake.

TwinsofMLB · 11-05-2009, 02:08 PM

Sounds like one or more cylinders isn't firing.

dondomman · 11-05-2009, 02:54 PM

sorry if someone already answered this i didnt have time to read everything but i wanted to help a fellow polaris rider uhh you said you primary engages but your belt just smokes? coulde it be that your seconery is seased or possilbly your geared to high to spin the track alought in that case it should spin on the stand anyways good luck

mrholmquist · 11-05-2009, 06:04 PM

a couple of things I am thinking about.......

You don't mention it but I am sure you did a compression test and found that to be ok?

You said the center cyl is spitting back through the carb?
That is a piston port engine so the bottom of the piston (skirt) is supposed to close off the port when the piston is in position. Remove the carb and while slowly turning the engine by hand look at the skirt of the piston check to see if it is broken or scored. Compare it to the other pistons skirts.

The other thing you mention is that the belt stays engaged after you let off the gas????
one of two things is happening there , either the engine rpms are not returning to idle speed causing the primary clutch to stay engaged , or the primary clutch is sticking.

If the clutch stays engaged and the engine is returning to 1900 rpm like you stated above then the primary clutch is definitely in need of attention.

a third I dea I am going to throw out is the possibility of a rodents nest in your exhaust pipe restricting the flow at high speed. I once had a squirrel fill my exhaust system with wallnuts over the course of a summer

staycoolgb · 11-06-2009, 01:04 AM

Could the problem be one of the floats in the carb sticking after the first try? Could be why you see some spraying out the carb. Then after it's shut down it would eventrually return to the normal. am I warm or cold on this. Please comment.

600BlairMorgan · 11-06-2009, 01:20 AM

How cold is it there? Could just be loading up at WOT only way to know for sure is look through spark plug holes. look at the top of the pistons and see if they are wet. After reving it out you say the track still turns. hit the brake put it back on the ground if it doesnt move theres probably nothing wrong.

XCR KDX NJ · 11-09-2009, 01:11 AM

While the sled is on the stand and after making the track spin, the clutch disengages but the new belt still rides the shaft and spins the track. If it were on the ground the track wouldn't spin. The idle is 1900 rpm and it goes back to idle after I let off throttle. The entire airbox is off, could this be making it stall back trying to hit WOT ? And also the temp is in the 50s.

The head pipe and muffler I had taken off to paint and they are clean on the inside, nothing clogging the pipe.

When the sled is started, all three cylinders are firing and it sounds like a triple.
When I apply throttle, slowly raising the rpms, the track spins when it hits 4000rpm and then I hit it, giving it WOT in a punch. IT screams and sounds and feels like it will go 100 in a field. I let off the throttle, the sled rpms drop to idle, and I do the same scenario again, but it wont scream and rev like it just did, it sounds like a deep mushy bellowing, with the rpm stopping at 5000 rpm when giving it WOT. Nothing is clogged in the fuel system, carbs are all tuned the exact same, clutches engage and disengage normally.

I had another clutch laying around from a xcr600 that was in working order last winter. I took the 650's off and swapped it with the xcr. It ran just the same.

mrholmquist · 11-09-2009, 08:41 AM

My mistake on the clutch thing , I was thinking you meant it was staying engaged. If you stop the track and it doesent cause the engine to labour then it must be releasing ok. Sorry.

The other thing it sounds like you are saying it revs fine once but if you try to rev it a second time right away it will not go to full RPM. Sounds to me like it cant get fuel to the carbs fast enough for sustained high speed running. Perhaps the fuel pump is pumping weakly? I mentioned this insufficient fuel supply as a possible cause to your issues in a previous post but did not touch on the fuel pump. Perhaps a kit in the pump
would be worth the effort they cost like 10 bucks.