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Engine Trouble Bogging engine, little throttle reponse

  • Thread starter SchwinnAlloySeven_GT5
  • Start date
S

SchwinnAlloySeven_GT5

Guest
Prologue
Well, I was out on a ride the other day,and all of a sudden there was a *pop* and the motor started decelerating. I hit the clutch and look down and my sparkplug is missing! Must have gotten loose and quickly unscrewed itself. I stop and backtrack and it's nowhere to be seen!

"That puppy must be in lower-level orbit" I think to myself. No biggie, I always carry a spare. However, upon installation, I find that the plug wire boot won't snap on! Seems that the plug had eloped with the contacts from the inside of the boot :eek:

5 miles from home, but this time that North wind is pushing me. Next day, I locate a new wire from the local motorcycle shop , install it, and all seems well...
-------------------------------------------------------

My Grubee GT5 starts quickly and idles well, like it always has. But now, when I try to accelerate, all I hear is bog. With no load, it will bog, too. The throttle does not respond very well and the motor seems to "4-cycle" at any RPM but idle. The motor acccelerates very slowly when you goose the throttle off idle, too.

I've checked all connections and bolts, tried another plug, another wire, different gas, all 4 settings on the Dax carb it's using, and the only time I noted a difference was on the lowermost setting. IIRC, that is the richest setting possible, and it ran slightly quieter at lower RPM - over 4000 RPM and it was worse. I put it back to the second setting.

Now the odd part: If I take the time to accelerate over 32MPH, the engine has power again and quits "4-cycling". What in thunder is going on? Carb? Magneto? CDI?

Please guys, I need help :(
 


G

gone_fishin

Guest
if it was running fine before the fiasco & you've replaced plug and wire, then changing carb settings is probably not the solution?

have you checked the exhaust for obstructions? intake air-leak? either of these could (possibly?) have occurred during the "pop"...just a guess, trying to help.
 
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SchwinnAlloySeven_GT5

Guest
The intake and exhaust gaskets seem to be fine. I have noticed an increasing bit of oil buildup around the exhaust baffle, though. I've always ran this motor at 20:1, which seems to be too rich according to many people's posts in this forum. This bog has always been there to a degree, but it is much worse now.

I have a spare magneto and a CNS carb. However, I am very confused by the new carb, so I haven't put it on yet. There are 4 vacuum ports on it and none of them have lines on them. No instructions came with the carb so I have no idea how it should be configured. :???:
 

azbill

Active Member
Joined
Dec 15, 2006
Messages
3,721
SchwinnAlloySeven_GT5 said:
The intake and exhaust gaskets seem to be fine. I have noticed an increasing bit of oil buildup around the exhaust baffle, though. I've always ran this motor at 20:1, which seems to be too rich according to many people's posts in this forum. This bog has always been there to a degree, but it is much worse now.

I have a spare magneto and a CNS carb. However, I am very confused by the new carb, so I haven't put it on yet. There are 4 vacuum ports on it and none of them have lines on them. No instructions came with the carb so I have no idea how it should be configured. :???:
I believe the vac ports are left open...just connect fuel line and mount choke lever
 
T

thatsdax

Guest
Better hope that...........

A lose plug allows fresh air into the motor. This causes a lean condition and can damage a motor. I hope that has not happened to your motor. Always check intake bolts, spark plugs, ect for tightness. Intake fresh Air leaks are devastating for a 2 stroke motor.
 
G

gone_fishin

Guest
which leads us (me, anyway) to "what kind of damage?"

scored cylinder, wasted rings, that sorta stuff? and how long does the lean condition have to exist to cause damage?
 
S

SchwinnAlloySeven_GT5

Guest
I've always checked bolts and plug before a ride. The day this happened, I had gone nearly 50 miles. Also, once RPMs are over 4000-4500, it will run normal with normal throttle response. It just takes 10 full seconds for the motor to finally rev that high! Now and then the motor will backfire or cut completely out, too. I do not have a kill switch.

Swapped out magneto - no change. Ordered a CDI just in case. CNS carb is on, but it got too dark to complete the setup. Those open vacuum ports worry me! I'll be testing it out tomorrow.
 
S

SchwinnAlloySeven_GT5

Guest
Finished up the CNS carb setup. Motor fired right up and has a little better response, but top end is gone and the exhaust smokes now. No amount of adjustment will fix it. Runs best with both screws turned all the way in. What a PITA :(
 
B

BikeHacker

Guest
I didnt read all of the responses so excuse me if i repeat anything. YOU HAD A MAJOR TIMING MALFUNCTION and the force of your piston meeting the explosion head on popped your plug. This could have killed you if the barrel had exploded like large dirt bikes do when they severely over rev. (70mph jumps) Pull your mag cover and look to see if your mag rotor has shifted or loosened on the crank. If so just knock it back on with an impact gun and your good. I put a mag rotor on backward once and it made that same detonation you mentioned.....
 
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