RS mechanical cam chain tension problem bulletin

[blustar]

Well, I ended up replacing my cam tensioner yesterday. It cost a bit to do it but I will sleep alot better knowing that I have eliminated that particular risk.

 

[jlparker77]

Holy cow, Blizzard. Even if you did happen to turn the clutch a little, it should not have been able to jump a tooth on the cam gears. I just can't imagine that what you did would cause a valve timing issue. I guess a compression test might give you an idea. I believe you will find something simpler that is overlooked.

 

[bluemissile]

if the primary was turned with the timing chain off it will throw thw timing off because you turned the crankshaft but not the camshaft. not sure of the procedure on these will involve a degree wheel or a dial indicator probably unless there are timing marks on all of the shafts to line up. good rule of thuml is to line up all components to timing marks or make you're own with a sharpie before removing any parts.

 

[canadianhunter]

Just got home from the dealer with our 2 sleds after our dealer installed the new tensioners. At NO COST due to a damn good dealer in Weyburn Sask. and Yamaha.
Asked the dealer if our sled were quieter and he was not sure, but as I unloaded them and drove around our yard I felt they were much quieter and smoother.
With a dealer like this it is very hard to consider other brands even though I do not see a current Yamaha in my shop, maybe something next year or the one after.

 

[Crewchief47]

I would doubt that the cams came out of time with a minimal amount of primary movement, especially if you're sure you took the old one out then immediately inserted the new one without moving anything. Would look for some other issue. Did you drain the bowls while taking the carbs off and lose the prime?

 

[Ground Blizzard]

Thanks for all the suggestions. After reading the posts I'm pretty sure that it's not a timing issue but I'm still at a loss. Again, replacing the tensioner was pretty straight forward just time consuming due to tear down and the tight space you have to work with. Fyi, it worked better for me to just loosen the front engine mounting bolts, instead of removing them, this way the engine pivots up and forward giving you a bit more room.

I do believe I'm seeing a side effect of another issue because of way the lights and gauges occasionally light up.... but what?. I did test the stator and got .5-.6-.6 but I can't find the specs for a rage to know if this is within spec. If I had a good dealer locally I'd just bite the bullet and take it in.

Please keep the suggestions coming. I'm about ready to dump the sled and move on. I have maybe 1500 miles on this sled and it's been one of those, if it can go wrong it has gone wrong deals. Anyway, thanks again for the suggestions.

 

[jlparker77]

Is it possible that the plug wires/coils are mixed up? i know that sounds simple, and I don't know if that matters or not on these engines. I know most two strokes fire all plugs at the same time. Also, I do have one of these vectors. How many people have actually had a problem with these tensioners actually failing causing engine damage? I know all about the hooplah around them, I would like to hear from people who had it fail.

 

[AKrider]

If the carbs are out of fuel it will take a long time to start the sled. Just take the tank vent hose loose (its in back of the secondary, above the foot rest) and blow some compressed air into the tank. This will pressurize the fuel system and force fuel into the carbs. The sled will start up pretty quickly after that.

 

[grizztracks]

3 things:

spark, fuel, timing

If you have spark the CDI should be good. The next step is to check for fuel. Check spark plugs to see if it's flooding (good time to install new plugs). If they are dry pull the air filter and give each carb a spray of fuel (I use a small spray bottle filled with gas).

If spark and fuel are present then you may have jumped time. If it moved far enough there is a chance it bent a valve (check compression). I don't have the manual for your sled but I'd think the timing procedure would be similar to other yamaha models. You can download the nytro manual: http://www.ty4stroke.com/viewtopic.php?t=58910, look under the engine, camshaft section for the timing procedure.

If all else fails, talk to your dealer. My dealer is always willing to discuss and help troubleshoot problems.

 

[Ground Blizzard]

Grizz, the information you provided was great, thanks much! My outlook is grim though. To answer the question "do tensioners fail", yes they do and I'm proof. I called the dealer this morning and, after much discussion, the tech was pretty positive that the valve train noise I was hearing was from a bad tensioner. He did say it is a rare occurrence though. More than likely the damage was already done before I replaced mine. There is always an outside chance I did something wrong but these tensioners are truly plug and play(tech agreed), they're just tough to access.

The really sucky part is he doubted Yamaha would cover anything since I'm the one who replaced the tensioner, but he'll ask. It sounds like my stator is also going.... I just can't see putting anymore $ into this sled. So I'm pretty much left with a parts machine. To say I'm disappointed doesn't begin to describe the way I feel. This has truly been a doomed sled.

 

[twomorestrokes]

I wouldn't give up just from an over-the-phone diagnosis, especially if it was running before the tensioner replacement. Noise or no noise, if it ran well before disassembly, the damage was not already done.

 

[grizztracks]

Hopefully your dealer and yamaha will help you out. I had a bent subframe on my nytro and it was out of warrenty. I took it to a dealer that I've never purchased from and they got Yamaha to cover it. You never know so don't give up.

Have you checked compression to see if it bent a valve?

 

[Ground Blizzard]

Grizz, I ordered a 10mm adapter for my tester so once that comes I can do a real compression test. My low tech testing and the visual differences in the heights of the valves says I have bent valves. But I'll have to wait until the part comes before I'm 100% sure.

2more, the tech was pretty sharp and ultimately the compression test will tell all. I do believe he's right though, the last time I ran the sled there was an occasional slight stuttering(along with the valve noise) but I figured it was fine and the stuttering was due to the old gas. In hindsight I think it was the beginning of the end.

 

[firedowg]

Would it be possible to remove the bolts and rivit I have circled and drop the exhaust sheild? then reach it from there? You could always replace the rivits or just use bolts in there place. Just a idea.

 

[jeffkinney]

Would it be possible to remove the bolts and rivet I have circled and drop the exhaust sheild? then reach it from there? You could always replace the rivets or just use bolts in there place. Just a idea.

Unfortunately, due to the placement of the cam chain tensioner on the backside of the motor, it is impossible to remove the tensioner without removing the rear engine mounting bolt and spacer. No way around it, you have to remove a lot of parts to get there.