Yamaha 350 4x4 Big Bear clutch issues or ???

[Bruce Sawyer]

1987 YFM350FWTB 350 4x4 Big Bear when going uphill will sometimes act like the clutch realeases then re-engauge all at once.

Seems to maybe be little more often if the engine is at about 1/2 throttle instead of at lower rpms.

I have the Factory service manual and checked the external clutch adjustment screw as ok and the H/L/reverse shifter lever linkage as adjusted correctly. It appears to be maybe a internal (inside the case) clutch issue or ??

This is the type Big Bear that has the manual shift lever on the left front fender and has the manual foot shifter lever with 5 speeds forward.

Can someone tell me how the primary and secondary clutch operates? 

I assume one is mechanical and one is centrifugal. (what I'm asking is one clutch for the higher rpms and one for the lower rpms or ???. (the clutch appears to only momentarily release at the higher rpms is why I ask. The cycle has about 3000 miles of low speed through the brush hunting and has been well maintained, oil changed, etc and no deep water or mud useage.

Anyone been into a similar issue with the big Bear ATV????

[Ajmboy]

Did you change the oil with incorrect oil by chance? The oil has specific additives for clutches.

Check out this topic: 

 

[Bruce Sawyer]

Original poster: Forest Gump.

 

I determined that I had been using the wrong oil in this ATV Yamaha machine for quite some time.

I should have been using a 10-40 ATV cycle oil for wet clutches. I was using regular automotive oil.

Automotive oil is slicker and will cause the secondary clutches (also termed transfer clutches) to slip.

 

ajmboy: If I were you I would change the oil to make sure it's the proper type and if that don't correct the issue you are probably going to have to checked you transfer clutches (secondary clutches) to see if they are burned and need replaced.

 

I'm not getting email notices in my mailbox even though I'm subbed????

 

[Bruce Sawyer]

I changed the oil to the correct type. ATV 4 cycle motorcycle 10/40 from Napa.

The Big Bear has been operating ok now with no clutch jerking.

I seen this you tube video for a Yamaha Big Bear about how to inspect/change out the clutches that will be very helpful to anyone going into the clutch area. The service manual will be good to use in addition to this video. You may have to C/P this link into internet explorer for viewing?

https://www.bing.com/videos/search?q=How+to+replace+the+clutches+on+a+Yamaha+Big+Bear%2c+video&docid=608041014883389422&mid=F1B989DC120398A44A80F1B989DC120398A44A80&view=detail&FORM=VIREHT

[Frank Angerano]

Good stuff brother. Glad to hear its running good! 
Ride safe.