I'm putting the top end back together with a TrailBikes 88cc cylinder but retaining the stock head. All is going fine until I try and seat the upper cam gear onto the end of the camshaft. There is not enough slack in the cam chain, to get the gear to seat and then bolt on to the end of the cam. I'm sure that the cam chain does not have some extra links wrapped around the crankshaft, so I cannot figure out where the cam chain slack went. I measured the aftermarket 88cc barrel and it is maybe .010in longer than the stock barrel. I have not fully tightened the head bolts but I don't think the gaskets will compress much more to make the difference. There is not an adjustable cam chain tensioner, right?