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Beating my head against the wall

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Hi Folks,

 

I could really use some help. I'm running out of ideas. I bought an 86 xr 250r from a guy on craigslist who said the bike was running fine a year ago but it only putters around now. The bike starts easily and idles fine but it has no power and it dies once you open the throttle past 20%. The bike also smokes quite a bit out of the exhaust which has a fair amount of corrosion and holes. When it is running the compression feels fine to me.

 

Here is what I have done so far to try to fix the problem:

1) Installed a new plug and I tuned the slow jet back to stock (2 1/4 turns) with the appropriate main jetting for around 5000 ft. - no change

2) I replaced the float because it was staying down and the fuel was over flowing - no change

3) I replaced the stator with a new 150watt stator from Ricky Stator - no change

 

Could this be a timing issue? Should I try seafoam fuel treatment?

 

 

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TOTALLY dismantle the carb and clean every orifice/passage. Replace every jet unless you can absolutely see zero blockage. Most people don't do a very thorough job of cleaning carbs. Clean the petcock strainer. Clean the tank. Install an inline fuel filter.   

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Try a new pilot jet. The old one may be partially clogged. Is the 86 a single carb or dual?

Signle carb. The jet didn't appear to be clogged as I could blow through it but I don't know if that's a legitimate way to test.

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Remove the fuel screw and clean that passage. Account for the spring, washer and oring before you go blasting it with cleaner and air.

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Is the smoke blue or black.

Sounds like needle jet issues. Since it idles fine I guess the pilot must be good.

Could it be running to rich on the needle/main jet? Hence the smoke if black. What colour was the plug?

Does it run better or worse with the choke?

My guess is it flooding on part throttle. Engine and timing is probably fine if it's easy to start.

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Is the smoke blue or black.

Sounds like needle jet issues. Since it idles fine I guess the pilot must be good.

Could it be running to rich on the needle/main jet? Hence the smoke if black. What colour was the plug?

Does it run better or worse with the choke?

My guess is it flooding on part throttle. Engine and timing is probably fine if it's easy to start.

The smoke is white in color and the plug is black.

 

It barely needs the choke to start and runs without any choke right after starting. If I turn the choke to full it will kill the engine. I took the carb apart completely and boiled it in hot water and then used seafoam carb cleaner to try to blow out the jets. All of the jets seem to be fine though as I can easily see and blow through them.

 

Running out of ideas.....

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It still sounds like it's running too rich. If you un-clip the air filter to lean it up does it run any better?

Runs exactly the same with the air cleaner removed. I also just spoke with the previous owner who seemed like a fair guy and he said it ran fine last summer but that he hadn't touched it since.

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Did you blow thru ALL the little passages in the carb body itself? Every single one of them? Did you install an in line filter BEFORE you started it after cleaning the carb. Did you remove the petcock and clean it and the screen? Did you thoroughly clean the tank?  

Edited by YHGEORGE

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I don't understand why it would start easily, run at idle but die under any load.

Since leaning it up didn't help, how about throwing a bit of fuel in the carb when warm, fire it up, open the throttle. Does that make it rev?

 

I doubt it is petcock or tank. I can switch off the fuel on my bike and ride around for about 4 minutes before it starts spluttering. Maybe the float level is very low however.

 

Not that I think this is the issue, but just to rule out have you given it a compressing test, checked the valve gaps etc.

If all is in check, I would be looking for a cheap second hand carb, swap them over and see if it behaves any difference.

Expensive way of elimination but should help you hone in on the issue.

 

To check the timing, at TDC (there is a mark under the big Allen key bolt on the left side) the sprocket bolt on the chm shaft should be at 12 o'clock. It may be possible to check this with one of the valve adjustment screws removed, otherwise, just take the rocker cover off. But again, I doubt it is a timing issue.

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Did you blow thru ALL the little passages in the carb body itself? Every single one of them? Did you install an in line filter BEFORE you started it after cleaning the carb. Did you remove the petcock and clean it and the screen? Did you thoroughly clean the tank?  

I did blow through all of the orificies with carb cleaner and it blew through the passages. I can't tell if it is impeded at all unfortunately though. I haven't installed any kind of filter or cleaned the tank. I don't see how that would affect performance with new fuel. Over time I would imagine it could affect it with gunk in the tank.

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I did blow through all of the orificies with carb cleaner and it blew through the passages. I can't tell if it is impeded at all unfortunately though. I haven't installed any kind of filter or cleaned the tank. I don't see how that would affect performance with new fuel. Over time I would imagine it could affect it with gunk in the tank.

Mine had some white "something" that continually came out of the tank and fouled the pilot jet almost immediately. I think the po had put some additive in the gas and it left a residue. The petcock screen was bad and did not filter anything. I finally discovered what was happening and put is a VisuFilter and it has been perfect since. Good luck.

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Choke is off in the down position. Choke is on in the up position.

If bike will only run with the choke lever up then your jets or fuel passages are clogged.

It will only run with the choke off or down.

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What did the compression read?

I haven't run the test yet. Once I get the results later this week, I'll post them.

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It will only run with the choke off or down.

This is correct. Pilot jet and circuit should be ok.

Could also be electrical. Clean all the electrical connections really well and put a smear of dielectric grease on them. Unscrew the spark plug cap from the spark plug wire and check it for corrosion. clip off a 1/4" and screw it back on. Plug caps go bad after a while and do not grip the plug as well as they should.

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Okay, 

 

I cut the wires for the spark plug an quarter inch and installed a new plug - No change

 

Compression test reads 150 psi. I ran this twice and got identical results.

 

Thoughts?

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