[IceFisherman]

Hey all, I'm getting a "bog" from 3500-4500 rpm's. Sled is a Yamaha Phazer 485 fan. Anything above 4500 rpms runs fine. One problem I am having, is that my tach cable at the oil pump is leaking. I'm just wondering if oil could have gotten into the primary clutch and if that could be causing the problem, or if it's the carbs. Compression is good, belt tension is good, track tension is good and everything is fine in the rear skid (bearings are good, torsion straps are good, etc.) Fuel is also good. I'm thinking it's one of 3 things.
1.) Primary clutch
2.) Carbourators
3.) Weak diaphragm in fuel pump.

What do you guys think? I'm not a snowmobile guru, and would hate to spend hours cleaning carbs, if it's more than likely the clutch. I have taken apart my secondary clutch, and replaced the plastic dogs hoping that was the problem, but it wasn't.

Thanks for your input.

 

[snofrog]

what are your engagement rpm`s

 

[FreezerBurnt]

tors?

 

[IceFisherman]

Not the TORS, bypassed that to check it. Engagement RPM's are 3200. If I hold the throttle so it stays between 3500 and 4500 rpm's, the problem persisits. As soon as I give it some more gas, it revs up and goes just fine. Top RPMs are normal at 7000. When I first get on the gas, the clutch seems to engage fine and the sled starts to move no problem, then it just bogs out until 4500 rpm. When I get on the throttle hard from a dead stop, there is no bog at all and it just winds out and goes. I notice it the most when on the trails, boggy when easing on the throttle. Unfortunately, due to crappy trail conditions, I hate like heck to be givin' er' all the time. Not only do I risk throwing up rocks, but it also ruins what little snow there is for everyone else.

 

[trailblazer]

Not the TORS, bypassed that to check it. Engagement RPM's are 3200. If I hold the throttle so it stays between 3500 and 4500 rpm's, the problem persisits. As soon as I give it some more gas, it revs up and goes just fine. Top RPMs are normal at 7000. When I first get on the gas, the clutch seems to engage fine and the sled starts to move no problem, then it just bogs out until 4500 rpm. When I get on the throttle hard from a dead stop, there is no bog at all and it just winds out and goes. I notice it the most when on the trails, boggy when easing on the throttle. Unfortunately, due to crappy trail conditions, I hate like heck to be givin' er' all the time. Not only do I risk throwing up rocks, but it also ruins what little snow there is for everyone else.[/b]

Given the above info, it sounds like it's a back shifting problem.
You might start with giving your secondary a good cleaning, checking the cam slider shoes, bushings and spring tension.
Being that you don't experience the bog with a hard WO throttle pull, I would rule out the carbs for now. That also says that your primary clutch is shifting out okay. Of course you should give it a good cleaning as well including checking the pucks, bushings and spring tension here as well.

When re-assembling, use a black permanent marker such as a Sharpie and draw 3 lines around the clutch sheaves from the centre straight out to the edge. Do several runs with your sled once you get it back together. Then check the lines. They'll indicate if you're clutches are shifting out all the way or not. Where your belt rides, is where the marker will be worn off.

Good luck and let us know how you made out.

Jeff

 

[91mx]

I don't know a lot about these sleds but a quick thing to check would be your low speed jets. Just make sure they are adjusted properly and evenly.(Again I don't know a lot about your sled and am not even sure if you have low speed jets you can adjust just trying to help)