Author Topic: Engine not revving cleanly under load  (Read 5810 times)

ttyR2

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Engine not revving cleanly under load
« on: May 20, 2012, 08:50:35 PM »
I picked up a pair of FL350's over the weekend. One has a dusted engine (air box boot wasn't connected all the way, had a 1/2" air gap). The other one is in good shape.

Low end throttle is good, but once you start to wind it out, it doesn't pull cleanly. It feels fat (sorta blubbery), as opposed to buzzy and unstable like if it was running lean. I'll do some plug checks this weekend when I have more room to run it full throttle for longer. Needle is in the 3rd groove, though I moved it to the second to lean it a bit (didn't make much difference). Main jet is #142. Air screw is 1-1/2 turns out from seated. I'm at about 1300ft elevation, 70deg F or so, fresh fuel, using Polaris semi-synthetic 2 stroke oil mixed 32:1 for now.

If the clutch system was in need of servicing, could it cause an engine to run like this by not shifting out properly? Or is this a carb issue.
« Last Edit: May 21, 2012, 07:30:07 AM by ttyR2 »

Factory 45

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Re: Engine not revving cleanly under load
« Reply #1 on: May 21, 2012, 08:04:13 AM »
I just tuned Lukes 350 this weekend...and after going slightly leaner than the stock setup for temp/altitude in NE...I came to the conclusion that his clutching will need freshening and a new belt before we fiddle with the carb anymore. Do a comp test just to be sure...138psi is what the manual says.

Try going just slightly leaner and see if it cleans out on a few long pulls...this would further the belt/clutch theory. If you are all stock you are just a tad richer for your altitude then reccomended. Try going 140-138 main and second needle clip to lean it slightly and try pulling a long pull...and do a chop to the plug. If it shows good or a touch lean and it still feels blubbery through the pull in the mid range...get into the clutching a bit and give it a fresh belt. My opinion at that point would be a shifting issue overshift=bogging undershift=screaming RPMs.

This of course is ALL said under the assumption you have cheched the carb and cleaned it...but if you can tell me jet sizes sounds like you did. :)

ttyR2

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Re: Engine not revving cleanly under load
« Reply #2 on: May 21, 2012, 11:47:37 AM »
I forgot about the old trick of putting a couple wide lines on the clutch faces with a Sharpie and seeing if the belt is moving out properly. I'll give that a whirl too.

hoodlum

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Re: Engine not revving cleanly under load
« Reply #3 on: May 21, 2012, 02:49:26 PM »
What type of air intake does it have? If it's stock and the filter is clean,remove the air box lid and take it for a spin....If this helps the problem,it's more than likely jetting...Just don't lean it out with the needle and jets before trying this,because you could quickly melt the engine.....
Hoodlum

ttyR2

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Re: Engine not revving cleanly under load
« Reply #4 on: May 21, 2012, 06:08:43 PM »
It has the stock airbox (not Klemm) and freshly cleaned/reoiled stock foam air filter. I'll try running it with the lid off, plus get one size smaller jet for testing this weekend (woot! can't wait for camping over memorial day!)

ttyR2

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Re: Engine not revving cleanly under load
« Reply #5 on: May 24, 2012, 08:10:57 PM »
Did some more maintenance and changed the drive belt while I was at it. The engine still didn't pull cleanly (or at all) above about half throttle. Pulled the air box lid off and it really came alive, so obviously it's running rich. It has a #142 main jet in it now. What do you figure pulling the air box lit measures up with? A #140? Or #138?

ttyR2

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Re: Engine not revving cleanly under load
« Reply #6 on: May 24, 2012, 09:43:50 PM »
Oh...and about those clutches. Both FL350's I have came with Comet 102C clutches :-) I was stoked when I found out.

hoodlum

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Re: Engine not revving cleanly under load
« Reply #7 on: May 25, 2012, 05:06:36 AM »
The safe thing to do is try both starting with the 140...If you dropped to a 138 right from the start,the results might be not so good....Look into doing a dual air intake too....This will help your performance considerably....
Hoodlum

ttyR2

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Re: Engine not revving cleanly under load
« Reply #8 on: May 25, 2012, 09:41:44 AM »
Do you know of a writeup on a dual intake setup?

hoodlum

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Re: Engine not revving cleanly under load
« Reply #9 on: May 25, 2012, 12:49:04 PM »
Not off hand....Does the oddy still have the stock snorkle on it? Years ago,I added another hose coming out of the other side of the box,up the cage,and attached it through the stock collector box that is bolted up high on the cage....I also cut the inlet holes in the collector larger as well to compensate for the extra air that would have to go through it....

Factory 45

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Re: Engine not revving cleanly under load
« Reply #10 on: May 28, 2012, 04:22:59 AM »
102's and COMET in general can be VERY tricky to tune and find parts for. They were recently passed around through a few big corporate buy outs. You will have to post the color spring and cam arm numbers...to see if your calibration is correct. Too much clutch weight and too little spring will make it over shift and bring the revs out of the meat of the power. Also beware the open design...they can easily pack up with trail nasties and it would be like adding the wrong weights.

Did the lower fins on the cylinder get lopped off on the clutch side...to be able to clear the 102?
Are either of your buggies making alot of chattering @ idle?

102c's are much larger than the stocker...and they used to sell a whole replacement driven clutch as well.
Polaris and Cat sell clutch rebuild kits with all the bushings and fibre parts...some of it works on comet.

The reality of the company is that while they were getting passed around in ownership...other clutches became more popular. So this got distributors in a position to SIT on older stock...so places that buy in bulk...chose not to invest in comet. Places like PU and up by me Automatic distributors are calling what they have the last of the comet stock...and wont re order.

Until the company (consumer parts corp.) gets it together and follows through with tooling new parts...we will be scrounging.

If you are having clutch chatter and a shaky idle...I can post some pics of what to look for. I have a few 102's and have gutted and rebuilt them for my Pilot.

ttyR2

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Re: Engine not revving cleanly under load
« Reply #11 on: May 28, 2012, 03:26:40 PM »
We just got back from a weekend camping trip and took the Odyssey along. We were at about 3500ft elevation and I swapped to a #140 main jet, clip in the second slot on the needle, and the engine is still running really rich. Jet black in the exhaust pipe and almost no color to the plug because it's very wet. That being said, once it warmed up, it ran like gangbusters. It brought a smile to anyone who took it for a spin. Now the suspension on the other hand....what a kidney buster. Gotta do something about that.

The idle is fine, doesn't burble or hunt around much, and the clutch winds out good when you get on it. I did put the Klemm airbox lid on it to help lean it out a bit, and even then, it still ran rich, running Polaris 2 stroke oil at 40:1 (it's all I had handy). I didn't run premium in it as I hadn't noticed that was necessary, but saw the service manual said to run it. The watercooled head did a good job. It was nice not having to worry if you weren't going fast all the time.

LiveWire

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Re: Engine not revving cleanly under load
« Reply #12 on: May 29, 2012, 06:15:43 AM »
The ability to get Comet clutches depends on the model number of the clutch. Certain parts are backed up. The N-1 cam arms for the standard 350 clutch are back ordered so they can't make the Odyssey kit right now. I have some old stock of them so I bought an uncalibrated clutch to put them in.

The driven clutch which I have in stock is no larger than the OEM clutch. Both it and the OEM clutch will open up enough to allow the belt to go down in farther when using the slightly larger 102C drive. However, with stock tires, the engine will never pull full shift out of the stock clutch let alone the 102C. I have hit 75 on GPS with 20" tires.