1978 Yamaha DT125E - Requesting Aid!

[RyanR]

Just watched a couple Youtube videos on the leakdown test. Very cool. All my riding buddies are on 4T bikes so it might take me a while to track down a tester.

[Twin-shocker]

Sounds like your crank bearings are toast! Dont bother to mess around with leakdown testing...............remove flywheel cover and checking for main bearing wear is to way to go here. Rebuilding the motor properly shouldnt be that costly, and parts are easy to find.

[PSchrauber]

I would too look up the bearings first as Twin-Shocker mentioned, just take off the ignition cover then try to push and pull flywheel forward and backward, sidewards and up and down.

If there is some play when pushing or pulling the rotor this is still OK, if there is play when you push / pull sideways or up or down then the main bearings has to be exchanged.

While you have the ignition cover off you can test the crank seals, start the engine and then spray some WD 40 or brake cleaner between rotor and engine case and rotor, when the idling will change than you have an air leak.

Just to mention:
The Yamahas have some weird sound expecially the 250cc engines not really healthy compared to other engines, the 125 normally don't produces so much ratteling noise.

Please check you intake manifold for cracks too, also check the reeds that are in the intake, there might be some issues too like corroded plates, ...

[RyanR]

Thanks for the info guys. I'll pull the cover off tonight and check it out and report back. I guess if worse comes to worst at least a full top/bottom end rebuild on this thing won't cost much, parts seem to be plentiful and dirt cheap.

[PSchrauber]

Originally Posted by RyanR

Thanks for the info guys. I'll pull the cover off tonight and check it out and report back. I guess if worse comes to worst at least a full top/bottom end rebuild on this thing won't cost much, parts seem to be plentiful and dirt cheap.

OK do it,

btw. when it looks like this you have a problem :

[JeffS77]

Originally Posted by PSchrauber

OK do it,

btw. when it looks like this you have a problem :

been there done that...atleast you can still the piston rings on yours

[webmonstro]

When you removes the oil pump line to the carb did you leave the inlet on the carb open?
if ou did you gave yourself a big air leak and that would explain the 4K idle

32:1 is the right pre-mix and you should have used it when servicing and bleeding the oil-injection system

For a leakdown tester go over to blasterforum.com and searce there the engien in the blaster 200 quad is related to yours
Nuno

[RyanR]

Originally Posted by PSchrauber

OK do it,

btw. when it looks like this you have a problem :

Ha! Thanks for the info. No new updates right now, been too busy with work. I should have some time to tear into this weekend and I'll post up everything I find. I found a new oil reservoir with the oil level sending unit in-tact on Fleabay so I should have that in my hands here shortly.