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Kit I bought NICHE 686cc 102mm Big Bore Cylinder Piston Gasket kit for Yamaha Grizzly 660 2002-2008

2006 Grizzly 660 engine rebuild. I am hoping to find out if my cam will work with my new cylinder and piston.

This atv was smoking VERY bad. I assumed it was the rings/cylinder due to the excessive smoke at all times… We were told it was a built engine when it was bought but didn’t put a lot a faith in that. I figured it had a Chinese big bore kit and that was it.
So I took it apart and discovered it has a 102mm JE piston in it. I was very surprised. At that point I realized it was an OEM jug too. I took it to my local machine shop and he ran a hone through the cylinder and you could see very distinct low and hi spots. He said this looks like your problem and since its bored to its max, your cheapest option is to get a Niche complete top end kit and send it down the road… so I ordered one.

Just to be safe, I ordered seals for the valve guides and this is where things started to take a weird turn. When I pulled out the first exhaust valve I noticed the inner spring was broken and then once I had the spring off I saw the valve guide seal was completely missing. GONE. The inner spring must have popped it off when it broke and it got beaten to pieces and exited down the timing chain opening. Anyway, that explains the smoke. I pull up the parts list to find a new inner spring only to find out the stock springs are single springs. At that point I realized these must be aftermarket, probably Kibblewhite dual springs. After this I figured I better look at the cam and to my surprise, it was a Hot Cam. This leads me to my question. The Cam is a no.5. Above that are the letters WW HCHE. I am concerned this cam might send the valves into the piston. The JE piston has cut outs for all 5 valves and is not as tall as the Niche piston. I called Hot Cams and the tech help said “yeah you can drop it in. Will be ok”. I just didn’t feel like he put much effort into that answer so I am wondering if anybody has used this cam on a stock engine or even better, with a NICHE big bore kit.
I guess the seller was telling the truth for a change, This thing did run pretty strong.

JE on left Niche on right


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