Only runs without exhaust; suggestions?

Rustynickel

New Member
Apr 9, 2016
5
0
1
Lafayette
Currently having issues with my bike only running without an exhaust. If I put a brand new exhaust on the bike wont even try to turnover. I guess im having air flow restrictions somewhere.

current status:
Engine runs without exhaust. muffler must be adding too much additional air flow resistance on top of some other unidentified weak point.

best guess:
I may have ran too rich gas oil ratio initially and caused a clog somewhere best guess

Steps taken so far include:
-fuel oil mixture drained and refilled with appropriate ratio before any of these diagnostics took place.
-swapped to an 80cc carb to attempt run. didnt help
-broke down the carb inspected float;good,inspected for debris;clean, verified clear jet holes.
-inspected intake manifold; clean
-swapped plugs
-swapped 3 different muffelers;never starts
-attempt no exhaust turnover. starts everytime.

items not checked/swapped:
-cdi
-engine internals
 

Larry Trotter

Active Member
Nov 26, 2017
153
35
28
72
That is a little strange. Are you sure you are not shorting out a wire when you attach the muffler? How about attaching the muffler without a gasket and then making it run with it loose and then tightening the bolts up and see if it stops. I presume you have tried blowing through the muffler to see if it is clear. Larry

PS Take the end off the muffler and see if it runs without the baffles in it.
 

Russell

Well-Known Member
Apr 19, 2009
1,258
103
63
MA
I don't have any ideas, but find this problem interesting. Will follow this to learn something.

Currently having issues with my bike only running without an exhaust. If I put a brand new exhaust on the bike wont even try to turnover. I guess im having air flow restrictions somewhere.

current status:
Engine runs without exhaust. muffler must be adding too much additional air flow resistance on top of some other unidentified weak point.

best guess:
I may have ran too rich gas oil ratio initially and caused a clog somewhere best guess

Steps taken so far include:

-fuel oil mixture drained and refilled with appropriate ratio before any of these diagnostics took place.
-swapped to an 80cc carb to attempt run. didnt help
-broke down the carb inspected float;good,inspected for debris;clean, verified clear jet holes.
-inspected intake manifold; clean
-swapped plugs
-swapped 3 different muffelers;never starts
-attempt no exhaust turnover. starts everytime.

items not checked/swapped:
-cdi
-engine internals
 

Chaz

Well-Known Member
Jun 3, 2012
1,004
69
48
Vancouver, British Columbia
A few quick thoughts/questions. What is the fuel/oil ratio you are using? What slot on the carb needle are you set at? Have you tried with the muffler but without the air filter? Have you been using the primer button on the carb?
 

Rustynickel

New Member
Apr 9, 2016
5
0
1
Lafayette
-Wires are tucked and wrapped clearing the muffler.
-To no avail, the air filter has been off since i removed the carb to inspect/clean.
-Jet needle is set in the middle notch.
-initial oil/fuel ratio was too rich, after draining and refueling with 30:1 for now.
-i attempted running the bike with a loose muffler, it would start and ran a bit but i blew the top side of the gasket apart from the pressure..lol

I'll attempt the following and post results:

1. leave new muffler attached, remove baffle test run.
2. adjust jet needle maybe?
 

Chaz

Well-Known Member
Jun 3, 2012
1,004
69
48
Vancouver, British Columbia
Try moving the needle clip to the top spot to see if that helps. Another thing to try is lower the float level as you may be flooding. Also try a size or few smaller jet. The needle slot setting is for fine tuning after you've dialed in the proper jet size.

Is this a new build or has it been running just fine until now?
 

Rustynickel

New Member
Apr 9, 2016
5
0
1
Lafayette
This build is relatively new, used to run fine. then one ride it felt like it was losing power the longer i rode it. Had to pedal to keep momentum after a certain point. So it seems as though something faulted.
 

Larry Trotter

Active Member
Nov 26, 2017
153
35
28
72
I think most things point to a clogged muffler. Don't confuse things by messing with the carb, the problem is on the other side. Larry
 

Larry Trotter

Active Member
Nov 26, 2017
153
35
28
72
So very strange. I would be wondering if you have a problem with compression and the slight back pressure is blowing by the rings to prevent it from running. You are right, 3 different mufflers, I think you can rule that out. Without the muffler does it really develop any power or does it just barely run? You could have the rings seized in the lands causing you lots of grief. Larry
 

Greg58

Well-Known Member
May 1, 2011
4,143
1,033
113
62
Newnan,Georgia U.S.A.
Loosing power tells me you have a blown gasket or seal, or maybe a broke ring. I would start by taking the head off and checking the head gasket, look for oil around the base of the cylinder, that's a common leak area. Remove the magneto cover to inspect the crankshaft seal behind the rotor, there is a seal on the other end of the crank as well. If you find fuel leaking in any of these places you have found your leak.
 

Rustynickel

New Member
Apr 9, 2016
5
0
1
Lafayette
Loosing power tells me you have a blown gasket or seal, or maybe a broke ring. I would start by taking the head off and checking the head gasket, look for oil around the base of the cylinder, that's a common leak area. Remove the magneto cover to inspect the crankshaft seal behind the rotor, there is a seal on the other end of the crank as well. If you find fuel leaking in any of these places you have found your leak.
Internal inspection will be the next step only part ive looked into so far is the magneto, its dry there so ill have to remove the motor and cheach the head gasket soon..