Hesitation and loss of power

skyzo · May 18, 2010

Hi, ive got a 76 CR250 that was recently just ifnshed putting back together. Before we took it apart, it ran fine, and had all of its power, but we wanted to restore it some and clean it up. We gave it a new fuel tank, cleaned carb ultrasonically, new fuel lines, new air filter, in line filter to grab any stuff from the new gas tank, and thats it. Now after starting it up again, it hesitates and has almost no power when even a small amount of throttle is applied.
The first thing I thought was that maybe it needs rejetted because of the new air filter, but air flow should not be a factor, because the people that owned the bike before me were not very tech-savvy, and didnt even have an air filter on the bike. They only rode it on asphalt roads but still.
New spark plug gapped correctly as well, but still nothing. If i turn the air mix screw on the carb all the way lean, it will run a little better but not much.
Any ideas?
Thanks

skyzo · May 18, 2010

I just tried setting the needle clip position at different heights and still no better. Its running WAY too rich, the spark plug is soaked.

Patman · May 18, 2010

Stuck float valve? Choke? Any idea what you current jetting is?

rmc_olderthandirt · May 18, 2010

Are you sure you put all the jets back in the carburetor?

I have been playing with the jetting on my bike forever. A few months ago I wanted to order up some new jets but I needed to know what I currently had in the carburetor so I took it off and removed all the jets so I could make note of what I needed to order. I threw the carb back together but didn't start the bike due to it being late. Then I loaded the bike in the rig preparing to head out for a district endruo.

I get to the riding area and the bike runs like crap. It would start OK but wouldn't rev up and just really lacked power. Sounds just like your situation.

I tear the carburetor back off and discover that I failed to put the pilot jet back in! ( I found it a few days later laying on the garage floor). Fortunately, I had another pilot jet, although it was a size richer than what I had failed to put in so I was able to get the bike running well enough to ride the enduro.

So, my advice is to make sure all the jets are in place.

Rod

skyzo · May 18, 2010

Alright, thanks guys for the replies. I checked the float, adjusted it to correct levels, checked choke, and cleaned everything really good again, and still same problem. Its actually worse now, it will only stay at about 800RPMs or so, and if any more throttle is applied past there, it just bogs down with a real deep rumble, and backfires like crazy. I will check all the jets tommorow, and will also take a look at timing im thinking.
Any other advice is appreciated, there is an event this weekend I was hoping on bringing it to, but not in this condition.
Thanks

mathd · May 19, 2010

Did you check the reeds?

skyzo · May 19, 2010

The elsinores didnt have reed valves until 78, so I missed it by a few years.

Im thinking the condition that its in right now, it is running too rich. The spark plug is always wet when I pull it, and it just bogs down all the time. So I'd assume this is just a carberuter air/gas mixture issue, but which jet would control this? Ive cleaned all the jets, but still same problem. Maybe one of them is misadjusted?
Thanks

sr5bidder · May 19, 2010

I would pull the air cleaner off and see if it acts better, if so start jetting smaller..

some one could have drilled the main jet bigger for the "no air filter mod"

also check the silencer for mouse nests ( don't know how long its been down)

Someone · May 19, 2010

Try removing the inline gas filter you installed.

skyzo · May 19, 2010

OK thanks guys, I just went outside and tried the things suggested.
Ran without air cleaner, and still same thing, no difference. Silencer is clear of any obstructions inside, and I ran it without the in line filter, and still the same thing.
I wish I could explain it better, it starts up and theres a backfiring/pinging sort of noise, and it wont go above maybe about 1000RPMs, and acts like its super flooded. Even after only running for 10-15 seconds, if the spark plug is pulled it is drenched in gas. When throttle is applied, it just gives a deep rumble and doesnt affect the RPMs much.
Before cleaning the carb and bike up, it ran fine, and that was only a week or so ago. So I definitely suspect the carb, just not sure what could cause this.
Thanks again

csdwarf · May 19, 2010

yeah, i know the rumble your talking about, my friends snowmobile did that and it ended up that it was just running rich because the choke, check your choke,i do belive your right about it being rich tho.

2strokerfun · May 19, 2010

I had to finally toss the old keihin and buy a 36mm Mikuni. The needle jet and jet needle were so worn it could not be jetted correctly. The Mikuni will drop right in on the elsinore. Another thing that can be causing this is a bad choke circuit. When you have it running, try moving the choke and see if it makes any difference. Did you ever check your timing??

skyzo · May 19, 2010

Thanks for the replies guys! on problems like these, it really is helpful to have a few other people helping out.
Just got done checking timing, it is spot on, also cleaned the carb yet another time to make sure everything is working. The floats are exact, float valve works great, all jets are perfectly clean. the only thing I have yet to try to test is the choke. It doesnt make a difference when I put the choke on when it is running, I think you guys may be right. What should I be checking for with the choke, just a stuck valve?

sr5bidder · May 20, 2010

I'm not familiar with the carb you are using, but another check you could do is let the carb fill up then shut the gas off then start the bike and let it run down the gas while trying to make it rev occasionally and see if it gets better or stays the same as the fuel levels drop, this test can eleminate timing/ electrical problems.

if your carb has the plunger type choke (fuel enrichment circuit) you can check for a bad rubber seal at the bottom of the plunger.

2strokerfun · May 20, 2010

sr5bidder said:
... shut the gas off then start the bike and let it run down the gas while trying to make it rev occasionally and see if it gets better or stays the same as the fuel levels drop, ...

Be prepared to engage a gear and pop the clutch to kill the engine if do this as engine can run away when it gets to a certain lean level as fuel level drops and the kill switch sometimes won't kill it.

if your carb has the plunger type choke (fuel enrichment circuit) you can check for a bad rubber seal at the bottom of the plunger.

It is a plunger type choke.
One other area to check is for a worn slide in the choke. That can also cause this problem. Might not hurt you to buy a used carb on ebay or www.honda-elsinore.com swap meet section.

skyzo · May 20, 2010

Wow, this problem is really starting to frustrate me. Took apart the choke this morning, and everything in there looks good, no wear, all seals intact, etc. Also took a look at the needle and needle jet, and both are in good condition. I just can't understand how it was working fine just a week ago, and now its completely unusable. This morning when I tried to start it, it bogged down so bad that it wouldnt even run for more than 5 seconds. Spark plug is just drenched when I pull it even after kicking it over only 5-10 times.

Something is seriously wrong here. What electrical could cause this?

sr5bidder · May 20, 2010

if you had painted the frame clean off all grounding pionts for the electrical system.

have you tried cutting the fuel valve off and running it down on fuel?

do you have an exhuast plug inserted in the tailpipe? :laugh:
...done that one!!

sr5bidder · May 20, 2010

have you backed the airscrew out any yet?

when you adjusted the float level did you set it to just touch the springy pin in the middle of the fuel valve? or did you hold it completly upside down for your measurements?..

..you got to kinda hold the carb sideways to tell when it begins to hit the needle vavle

hell if all else fails I'd set the level lower than specs (floats would be higher when viewing with carb upside down) to see what it does.

skyzo · May 20, 2010

Thanks for the replies sr5,

I have tried turning the fuel off and keeping it running, but all that happens is that it all of the sudden it turns off, no difference in RPMs, just keeps bogging until it dies.
Now it will only stay running for about 3-4 seconds before turning off, and there is no throttle response whatsoever. Ive tried the airscrew at all different levels, and have set the float anywhere from 15-25mm (recommended is 20mm).

Do you think that improper grounding somewhere would cause something like this?

Thanks again

skyzo · May 20, 2010

So I'm starting to think that the problem may be something with the stator. Its almost impossible to start now, and may only start up once every 10-15 kicks. When it does start, only starts for about 5 seconds before bogging down and dying. That is the part that still has me thinking it may be the carb.

Something that might have thrown something out of adjustment, was right before we started cleaning the carb and everything, the last time it was running, someone got caught on the throttle and red lined it for about 3-4 seconds, and we hurried up and turned it off, and then started cleaning stuff.

I really hate throwing money into this old bike, but I would love to get it running again.

Someone · May 21, 2010

Your scenario reminds me of my buddy's 99 RM250 rear brake problems. We did EVERYTHING to this guy's rear brake. Bled it many times, rebuilt the master cylinder, replaced brake line, completely cleaned out the caliper, etc, etc... It would still eventually lock up when riding after 20-30 minutes and we had to bleed the brake (on the trails) for it to release. Then he bought a used complete assembly(master cylinder, line, caliper) for the bike for $50, we put it on, problem solved. We wasted HOURS and HOURS working on this problem, and the thing that fixed it ended up being cheap and easy.

2strokerfun · May 21, 2010

how's the rubber seal on the top of the slide cover? After 34 years, they can be loosy goosy and hard to properly seal when you screw the top of the carb on. Sure your slide is returning all the way to the bottom?? Throttle cable adjusted with just a tiny bit of slack? Idle screw all the way out to start adjustments from??

skyzo · May 21, 2010

OK, this morning checked the rubber seal, made sure the slide was going all the way down, and both of them were fine.

Im really confused.... :bang:

I checked the timing again, and it is right on. Im starting to think this carb hates me

whenfoxforks-ruled · May 21, 2010

A really bad right crank seal, float valve, float installed upside down, or a sheared key on the rotor. You can take the nut and washer off the rotor and see if the slots are still lined up. The seal would need a leak down test. And the carb, look twice? Vintage Bob

rmc_olderthandirt · May 21, 2010

whenfoxforks-ruled said:
float installed upside down,

That is a good one to check. I managed to get the float installed upside down once. Makes a BIG difference in the float level.

Rod

Hesitation and loss of power

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