DT85 Not firing on Cylinders 2&3

[boroman]

I am due to start work again on my Suzi 1982 DT 85.

Had a problem last year that it did not fire on the bottom two cylinders, The motor went for a service and the guys said that they though it was a problem in the crank case causing pass over?or some thing like that. However this would suggest that fuel was not getting into the bottom two cylinders, this is not the case. When the engine has run the bottom two plugs are wet.

What i did notice last year was when I held the HT leads to check the plug spark, when holding the top lead you could feel the pulse, however when holding the bottom leads this was not the case. I did not want to totally abandon the motor so have aquired two coils to replace the bottom two and will be checking the motor again tonight.

Any suggestions on how I could check for some sort of failuer in the crank?
Compression on all pot 140-143 PSI

Thanks in advance guys

 

[boroman]

Re: DT85 Not firing on Cylinders 2&3

Update on engine works

Put the fuel and battery to the engine, went to start it it was very laboured, seemingly the starter motor was struggling to turn her over correctly. SO replaced the battery leads from the battery and beefed up the connections from the relay and grnd to the engine body.

Removed the plugs to check them, and span the motor to check for sparks (all three sparks good), without the plugs in the motor span freely, put the plugs back one by one and span each time. With two plugs in 1st and 2nd pot motor started, stoped the motor put the 3rd plug back and the starter motor laboured again , however the motor started. I did not have the muffs on so switched it off and attached them, then when trying to restart the same thing happened the starter motor did not seem to have the power to crank the motor properly.

The starter motor is getting hot, thinking it may be a problem with this unit?

Did notice when cranking the motor using a spanner connected to the fly wheel nut, that there is a bit of a stiff spot on the third crank? any ideas what could be causing this?

I am intending to strip the starter motor and check the unit, any body have any ideas how to check the integrity of the starter motor, I have a quality multi meter to measure resistance etc.

Any help or suggestions you guys can give will be gratly appreciated

Thanks

 

[boroman]

Re: DT85 Not firing on Cylinders 2&3

Further update

Stripped the starter motor, noticed the stator ring had carbon buildup. Sanded this back to bright and cleaned all the grooves. Bushes are tight and plent left on them, reassembled having cleaned the inside of the motor.

When reconnecting to the engine, cleaned the +ve and -ve connections.

When turning over motor spann alot better and the engine started, couple of early bangs then into life she went, was able to rev the engine and sounded ok. Trouble is I was doing it in my garage and can no longer carry on. I am going to move it to a better ventilated area, so I can check she is firing on all cylinders. Is it safe to disconnect plug leads to see if she dies when one plug is removed? Dont want to damage the new coils I have just fitted.

I will keep posting hope you guys can offer some insight

Thanks

 

[boroman]

Re: DT85 Not firing on Cylinders 2&3

HI

This is starting to feel more like a diary of events rather than a request for help.

OK so moved the motor to the door of the garage and started her up agian, Kept her running on the muffs for a while befor attempting to remove the HT leads from the plugs to check if there was any problems with any cylinder. This was the moment of truth, previously I found that when I removed the top cyliners plug the motor stopped as it was running on this cylinder alone. So I started by removing this plug connection first and the motor ran without fault and bearly missed a beat (Sucess, so my diagnosis of poor coils seems to be correct) I continued removing Plug leads in varoius sequences and the motor did not faulter, so it appears everything is fine with the firing.

However after a while the motor began to splutter now and again, when I applied the manual choke it ran fine, but when I attempted to throttle up it bogged and died. It looks like I need to strip them carbs again. I think once I have completed this I am going to take it to the shop to have it properly set up by the mechanic (someone with a bit more knowledge than I for tuning motors)

Once again I will keep you posted, hope some of what I have written may be of use to someone.