CR80, fouls plugs, blubbers at high speed

Gary B.

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#1
My son's '97 Honda CR80 recently developed this problem. Bike is all stock with the exception of Boyesen reeds. The jetting is already on the lean side (#122 main, 2nd groove on needle, 2-1/2 out on air screw) has fresh gas, HP-2 @ 32:1. I did find rust on the coil mounting bolts and frame, cleaned the fuel filter, checked all electrical connections, inspected the carb and reeds. I'm planning on ohm testing all electrcal components, maybe tonight (yes, I have a factory manual). It may need a top - end rebuild (could this be my problem?) it's been at least 15 tanks of fuel since rebuild. BTW, bike is used for trail and play riding only. I won't be able to check posts 'til tonight, so thanks in advance.:think
 

Brian

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#2
Do you run the bike out of gass before storing for more than an hour? Mine is prone to foul plugs if I don't do that.
 

Gary B.

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#3
Thanks for the tip, although I've never had this problem until recently. Do you suppose your needle/seat is leaking?:think
 

NdKxRacer

#4
We had a problem like this lately and it was a broken/chipped reed. It is easier to start there than to pull the engine apart. Make that your last option.
 

Gary B.

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#5
I already had the reeds out and looked at them. They're Boyesens and looked OK. Is there any easy way to check a crank seal? I was wondering if this could be my problem, even though the trans fluid level isn't low.
 

NdKxRacer

#6
Don't know and I guess you might check compression to see if it is low, clean the carb, try a new plug, spray starting fluid on the outside of the cyclinder and look for changes in the RPM's might suggest an air leak on a gasket.
That's all I know to look for.
 

125 rider

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#7
Like the post above said, check the compression. It may very well be that it needs a fresh top end. Did this come on all of a sudden or gradualy?
 

Gary B.

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#8
This came on rather suddenly. I don't have a compression spec, so I don't know how "low is low". I did spray carb spray all over motor while running without change. I also have had the carb apart and didn't find anything. Bike is on it's 4th spark plug and I went from a BR10EV to a BR7ES just to try. Next thing I was to try is dump the gas & try again. This is getting really frustrating!!!!!:scream:
 
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#10
What color is the smoke? is it smoking excessively? Does it back fire on start up any? Does the plug look rich in color? Is there any water in the oil or coolant? Maybe the gasket has blown internally. Its had about 15 tanks ran threw it so thats about 2-3 hrs per tank so around 30-45 hours on the top end. Its also possible the ring is toast. make sure all the fuel line hoses and the crank case breather hose are unclogged. I hope the fliter is clean and not the oem one still. I really doubt its electrical. if it was a bad main seal it would just be running really rich and be loading up on the bottom end and could get burbly and refuse to clean out after a few good rev's. A bad main seal won't really make it run like crap on top it can but its not a constant thing more like once in a great while. Maybe the reeds have hair line cracks but that usually makes the bike hard to start. I think you'll be better off checking out the top end.
 

Gary B.

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#11
It's mostly blue (oil) smoke. Yes it does pop back when you try to start it, but only after the plug is fouled. The plug is black and wet. It has a White Bros. filter, but had this problem with no filter installed. It starts easily with a new plug, idles and warms up OK, but as soon as you crack the throttle it blubbers and fouls the plug. At best you can rev it, but it really has no top end.
 

Gary B.

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#12
HEY!!! I think I figgered it out! I finally brought home my compression tester from work. Bike only has 50 -55 psi. We'll be takin' it apart later (when the kid finds the money). Thanks to all who replied.
 
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#13
Gary B. said:
HEY!!! I think I figgered it out! I finally brought home my compression tester from work. Bike only has 50 -55 psi. We'll be takin' it apart later (when the kid finds the money). Thanks to all who replied.
We have a CR80RB what would be a good compression tester ? Brand names .
We also have a KTM SX65 , and CRF230F ideally one that will werk on all the bikes if possable ...