79 250 OR Timing?

[Dwarf66]

The bike ran perfect all season. Today it ran flat like the timing was off. Starts fine. Idles fine and free revs. Ran ok but the hit is gone. Plug color perfect as usual. Flywheel key and stator in time and tight and clean. Carb clean. I drained and put fresh fuel. Still flat all day. I could ride around all day but will not pull hard. Only thing I have not checked is the pipe and silencer. Will a motoplat get weak and act like this? The last motoplat just would not start occasionally and then never started again but ran fine until it quit. Any ideas?

 

[dmcoz]

The bike ran perfect all season. Today it ran flat like the timing was off. Starts fine. Idles fine and free revs. Ran ok but the hit is gone. Plug color perfect as usual. Flywheel key and stator in time and tight and clean. Carb clean. I drained and put fresh fuel. Still flat all day. I could ride around all day but will not pull hard. Only thing I have not checked is the pipe and silencer. Will a motoplat get weak and act like this? The last motoplat just would not start occasionally and then never started again but ran fine until it quit. Any ideas?

Check your muffler core is blocked with carbon build up.

 

[84scrambler]

Maybe give a look at the throttle and cable, and make sure the your clutch is not slipping and check cable too.

 

[justintendo]

does the exhaust sound the same? check muffler for obstruction, something could have broken and could be blocking things. verify bike still goes full throttle too..if compression gets weak bike will run rich up top usually.

 

[Jeff B]

What was the outside temp. A bike jetted perfect for summer will be lean in the winter. Lean usually runs flat like you describe. Jeff

 

[justintendo]

or a sudden airleak like a cracked boot or seal

 

[Dwarf66]

does the exhaust sound the same? check muffler for obstruction, something could have broken and could be blocking things. verify bike still goes full throttle too..if compression gets weak bike will run rich up top usually.

No sounds alittle like it is loaded up. I am thinking an exhaust issue also. I am going to pull the pipe and silencer to see what is going on. At one point it woke up a couple of times for a minute or so then stayed flat the rest of the day. I was planning on getting a new carb intake boot and replace the right side seal also.
Thanks

 

[suprize]

new plug?

 

[justintendo]

new plug?

never hurts! check the cap too...if its the original motoplat cut it off and install ngk

 

[Dwarf66]

OK guys this is the important thread response. I found and fixed the problem. Looks like three pieces of inner wall from the pipe plugged the entrance to the silencer. I shook and tapped the pipe and there is nothing rattling now. I assume that the pipes are double walled as it is heavy and after 36 yrs there is some fatigue.

 

[Jeff B]

Good Deal. Yup...some of the off road models had double wall exhaust. Now you have to decide what to do to keep it from happening again. Friend of mine had a 390, did the same thing. He cut a window and removed the metal that was flopping around and had it welded back up. I read this site all the time just for valuable information. A lot of smart people here. Jeff

 

[Dwarf66]

Yea I have cut my Suzuki pipe in half to remove the screen but not sure if I want to cut my Husky pipe as I don't know where or how much is the inner wall. Will a 390 pipe fit a 250?

 

[justintendo]

Yea I have cut my Suzuki pipe in half to remove the screen but not sure if I want to cut my Husky pipe as I don't know where or how much is the inner wall. Will a 390 pipe fit a 250?

way different pipe