First timing belt job on a 420a, and it makes the 4g seem like cake.:|

I've installed the mechanical tensioner from partsdinosaur, and I've realized that the pulley on the mechanical tensioner is larger in diameter than that of the pulley on the hydraulic tensioner. I don't know if that's ok, but it did cross my mind.

Anyway, no matter what I do to remove all the slack in the timing belt, I cannot for the life of me get the timing belt to slide over the tensioner pulley. I start at the crank sprocket and go around CCW until I get to the tensioner, but I just can't get it to slide on! I've read that it takes a 'bit' of muscle to get the belt on, but seriously I'm giving everything I've got, and it's not budging. And it's not like the belt has a ton to go either. I'm talking MAYBE 1.5mm, if that and I CAN'T GET IT TO STRETCH OVER THE PULLEY.

For the record, the belt is the t246 150 tooth belt that comes in the kit from partsdinosaur.

Has anyone else run into this problem?

Have you modified the timing belt cover prior to install?

As far as the pulley being larger, I do not remember that to be honest. It does not sound right though. Been a bit since I have opened the front case of a 420a up. Call Bruce at Parts Dino up and ask him.

Dave, I think he is right. The mechanical tensioner pulley is bigger, just by a few hairs.

O.P, of course double check everything down there & any obstructions.

But you can try turning the intake cam a half a tooth "retard" Before you slip the belt over the gear, then when you get it on the intake cam, next would be the tensioner, it should pull that half a tooth back, & cams gears will aling at TDC. Hopefully allowing you the last of the slack the belt has to offer.

It can be a PITA with the mechanical, but you'll get it.

BTW, you have the correct belt, it uses a 246 belt on Mechanical Tensioner & Hydraulic.

I loosen the idle bearing up so it can be tilted and it gives you just enough to easily put it on. Then tighten its bolt up and tension it.