JR80 pops & backfires

T

The Honda Pilot

Member

Feb 25, 2001

394

1

• Aug 9, 2017

• #1

I've got a suzuki JR80 that I use for cruising around my property as a pit bike. It recently started to pop and backfire randomly and now it is physically not ride able because of the popping.

The bike still starts up first kick and will idle but as soon as you twist the throttle it will pop/miss and then backfire out the exhaust. Once it backfires it usually stalls the engine.

From research online I've heard that most of the time when a 2-stroke does this its a sheared key on the ignition. I popped off the ignition cover and all looks to be well in there. No metal shavings and I can still see the key intact.

Could it be a bad coil? Want some guidance here before I start buying parts. And no I haven't checked the compression yet. The top end has less then 5 hours on it.

 

truespode

Moderator / Wheelie King

Jun 30, 1999

7,980

249

• Aug 11, 2017

• #2

Stupid question but have you checked the gas for water? Does it have an oil injector? I would double check all of that for condensation.

 

T

The Honda Pilot

Member

Feb 25, 2001

394

1

• Aug 14, 2017

• Thread starter
• #3

I took the oil injector system off years ago. But haven't checked the fuel! I should though...

I did change the spark plug & dropped the fuel bowl to clean it out.

 

Okiewan

Admin

Dec 31, 1969

29,555

2,237

Texas

• Aug 16, 2017

• #4

So you are premixing then ... how old is the gas?

 

jaguar

~SPONSOR~

Jul 29, 2000

1,503

82

South America

• Aug 18, 2017

• #5

you looked and saw the woodruff key and assumed all is well. You can't tell by looking. You have to take it apart.

 

T

The Honda Pilot

Member

Feb 25, 2001

394

1

• Aug 22, 2017

• Thread starter
• #6

Okiewan - The gas is roughly 2-3 months old. Non ethanol 91 octane and castor 927 @ 40:1.

Jaguar- You are correct. I guess I will dig a little bit further.

 

jaguar

~SPONSOR~

Jul 29, 2000

1,503

82

South America

• Sep 4, 2017

• #7

Also if the head gasket is leaking those symptoms can happen

 

T

The Honda Pilot

Member

Feb 25, 2001

394

1

• Feb 5, 2019

• Thread starter
• #8

Update:
Tore down engine for top end rebuild. Sent the cylinder to local motorcycle machine shop
They bored the engine I think it was 10 thousands over and supplied me with correct size piston/rings.

Installed piston/rings new gaskets and assembled. Still experiencing same issue! I thought it could be broken reeds so I tore the motor back down (unfortunate design, reeds are on the underside of jug) And put new boysen reeds & new gaskets again. Start engine up and same issue.

 

T

The Honda Pilot

Member

Feb 25, 2001

394

1

• Feb 5, 2019

• Thread starter
• #9

I'm thinking of putting in new base gasket as I re-used that paper gasket the last time I put it back together. New headgasket each time I tore it apart. If the backfiring doesn't stall the motor it will start to run with a higher idle almost like it's running away. I'm sure that's a sign of an air leak. But could an air leak also cause it to backfire out the silencer and airbox?

 

T

TJW78

Member

Jan 3, 2020

10

1

• Jan 3, 2020

• #10

Have you checked the reed valve?