Vintage Dirt Bike Q & A

spent most of the afternoon getting those phillips head screw loose so i can split the cases. i did'nt think a couple of them were going to turn loose.

question on engines. i bought a spare engine that is supposed to be the same as my 1974 mt 125. but the crank has a nut that holds the flywheel on instead of a bolt through the center. plus some idiot cracked the inner part that goes against the crank. did they use different cranks or could this be from another model.

I found that using an impact driver makes screw removal pretty easy as long as the heads aren't already buggered up and you use a proper fitting phillips head bit.

The MT-125 has male threads on the end of the crankshaft and uses a nut to hold the rotor (alternator) on.
The CR-125 has female threads on the end of the crankshft and uses a bolt to hold the rotor on.

I'm pretty sure that the cranks are interchangable other than the attachment method for the rotor.
Look at the parts diagrams on a web site such as Bike Bandit and compare a CR-125 engine diagram to an MT-125 diagram to see the difference.
(Note that Bike Bandit part numbers are not real Honda part numbers, They make up their own part numbers for some reason)

I recently found a very cool website that sells Japanese tools. One item that I was very interested in was
the impact phillips head screwdriver. The modern CRs I work on have a bearing retainer plate right up against
the case wall and a regular impact wrench won't fit in there. This impact phillips head works like a charm.
In addition, the shape of the head is designed to work with Japanese style phillips head screws (JIS). Seems they
are a little different shape than what we use here. This tool is now part of my collection and is great at breaking
loose the case screws on my vintage CRs without buggering up the threads. They come in three sizes, the large
size is perfect for case screws. Here's the link:
http://www.levelchrome.com/Vessel-980-M ... p_173.html

dogger

_________________
1973 CR250M
1979 CR250R
1993 CR250R
2008 CR500R
2009 CR250R

I would of thought the cranks would of been opposite. As far as i know my bike is original . it has the hole for the bolt for the crankshaft. i know it was bought used at a dealer around 1976. guess they could of changed the crank.