97 CR 250 troubleshooting

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11/2/2017 5:01 AM
Edited Date/Time: 11/2/2017 5:19 AM

I just picked up my first dirtbike, a 97 CR250. When I bought it, the guy said it needed a new top end and it should be ready to ride, so I had a guy I work with help me redo the top end. He said there was a little bit of scoring on the jug but nothing to bad., just may have to replace it in the next rebuild.

Now the problem I'm having is, if the bike doesn't start within 5 kicks, it floods out with no throttle input on kicking.. once it does start, it won't idle, once it's warmed up it acts like there isn't any power sometimes and after it's warmed up it won't start back unless it's roll started down a hill big enough to clear it out for a few seconds.

I'm not sure what all is done to it motor wise other than a FMF Gnarly exhaust. I pulled the carb off last night and cleaned everything with carb cleaner, but didn't get it back on yet. The jets appear to be stock. 175 main, 55 pilot, needle is 3169N (or 1369N I can't remember) and clip in the 3rd position at 1,200 ft. The power jet screws where stripped so I didn't get to look at it and I didn't have a wrench handy to pull the choke out.

While I have the carb off, is there anything else I should be checking or am I in the wrong direction on where I should be looking? Thanks for any help.

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11/2/2017 5:48 AM

Look at:
Reeds
When you had cylinder off, did you look at powervalve to make sure all is well? When installing cylinder, you sure you lined actuator up right? If powervalve is messed up, it would still start the same, just not run good.
You reeds should seal against the reed block. If they are chipped, broken, etc, that will do all kinds of weirdness, flooding one of them.
Also, you carb has rubber inside it that carb cleaner will ruin. Only use carb cleaner on metal parts, not plastic/ rubber.

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11/2/2017 6:17 AM

Byron909 wrote:

Look at:
Reeds
When you had cylinder off, did you look at powervalve to make sure all is well? When installing cylinder, you sure you lined actuator up right? If powervalve is messed up, it would still start the same, just not run good.
You reeds should seal against the reed block. If they are chipped, broken, etc, that will do all kinds of weirdness, flooding one of them.
Also, you carb has rubber inside it that carb cleaner will ruin. Only use carb cleaner on metal parts, not plastic/ rubber.

I'm not sure if he checked the power valve or not. If he didnt, would I have to pull the jug to check it?

I'll give the reeds a check today.

I pulled the rubber gasket and o ring on the float bowl before cleaning

Thanks.

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11/2/2017 1:39 PM

I think I've found the problem. The reeds aren't closing all the way and one is broken in half. I'll order a replacement and see if it fixes it.

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11/2/2017 5:18 PM

For future reference, you can check the powervalve operation on that bike by removing the 17mm nut on the left side of the cylinder. Once the nut is off, start the bike and rev it. You should be able to observe the powervalve rotate open and close through it's entire range of operation relative to the revs. The powervalve on those years CR250 was susceptible to sticking if you run oil that causes lots of carbon or don't clean the valve well when the top end is apart.

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