Yamaha 8HP 4 stroke OB. Change timing belt?

[Barny55]

Hi ProDave. Sorted problem. No throttle return spring. If you can remember if an 8hp and year would be fab. Many thanks.

Just read your full post Pro Dave for hp rating. You did a super job on the engine as she fired first pull after resolving throttle return. Thanks again.

 

[ducked]

Is there specific provision for immobilising the crankshaft when undoing the pulley bolt? There wasnt on my Daihatsu Skywing, involving some pretty desperate improvisations, with the nagging doubt that the bolt might be reverse threaded (It wasn't, just ludicrously tight)

The manual said "Jam it with a screwdriver, because we believe in miracles"

I dont like OHC engines with timing belts. Hopefully I wont have another one

This specific desperate improvisation in fact referred to the camshaft bolt, though there were many others.

 

[jamie N]

One way of replacing a cam belt is by using a Stanley knife to slice the belt in half 'longitudinally', leaving one half in place, and removing the 'outer' half. Then slide the new belt onto the exposed 'toothed wheel' and cut the old belt off, then slide the new belt fully on.
This removes any danger of the cam slipping by a tooth either way.

 

[ducked]

One way of replacing a cam belt is by using a Stanley knife to slice the belt in half 'longitudinally', leaving one half in place, and removing the 'outer' half. Then slide the new belt onto the exposed 'toothed wheel' and cut the old belt off, then slide the new belt fully on.
This removes any danger of the cam slipping by a tooth either way.

Neat.

I cant now remember if there was anything that would prevent that on that car,but I dont think I'd heard or thought of that one, and will certainly bear it in mind.

Must be quite difficult to slice a cambelt, but perhaps one could use a Dremmel for most of it and just use the knife to cut into the tooth grooves from inside?

 

[Challenger.33]

I have taken the flywheel off this morning, it came off quite easily with my normal 3 leg puller without damage.

View attachment 167468
Changing the belt looks easy. The timing marks on both pulleys are clear. One magneto coil will have to come off and the thermostat housing, I want to replace the thermostat anyway.

so before i proceed I need to find a UK supplier of the timing belt, the thermostat, and a gasket for the thermostat housing.

Hi

Just to confirm that I changed the belt and thermostat on Sunday and this morning put the OB in the tank and ran it. All good.

It was really quite a simple job. I searched for the belt on the belt part number rather than engine type. Total cost just under £50 for belt, thermostat and gasket.

hi I have a early type f8 the one with out spin on oil filter . The belt they say to use seems way too tight . The later belt is to big . Could you tell me please what part number you fitted