Vintage Dirt Bike Q & A

I just picked up a 73 CR250M (or possibly 74) that's in 95% original condition, very low hours. Original tires and everything. Very good shape. I don't think its been started since '75 or so. I've cleaned it meticulously for a few weeks now. Dripped a little Marvel Mystery oil in cylinder to lube things up a bit. New air filter, plug, a few bolts, petcock rebuild, etc. I've ultra-sonic cleaned the carb, all jets, twice. Float level and operation look good. It's got great compression. Grounded outside the cylinder, the plug fires as blue as the sky. Thread it in and plug cap on, gas on, switch on, carb lever in start position... kick it over and over and over, tried rolling it off... it won't even hit. Nothing.

Just due to lack of time, I haven't tinkered with it again in the last few days. Next I'll pull the carb off again and just look into the passage between the carb and cylinder. Making sure there's nothing unusual there. I wouldn't think its off on timing that bad. But not sure.

I had a little desk time, so I figured I'd ask yall! What are yalls thoughts?? Is there something crazy obvious I'm overlooking? Any help and ideas would be appreciated. Thanks!

Can you smell gas at the tailpipe?

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

Sorry for the delayed reply, Ray.

The smell of gas at the tailpipe is very faint. Actually hard to say if any at all.

If there was barely any gas smell after kicking it a zillion times and pushing it, it's safe to say it's not getting enough (or any) fuel intake. With fuel, compression, and a good spark, you should get all sorts of popping and backfiring even if the timing's way off.

I wouldn't trust anything. Pull the fuel hose off the carb and check for flow from the petcock, check float valve operation with the fuel hose attached, etc.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

Thanks Ray. I'm going back to the float valve next. I've temporarily got a clear fuel line on it and I can see the fuel flowing into the carb. I'll keep you posted.

I appreciate the advice.

While I'm at it, I figured I'd add an "after" picture. After many hours of detailing. But no repainting. I wanted to leave it as original as I could. The picture probably makes it look better that it really is. It does have it's blemishes, no doubt.

The bike looks great! Sure you don't want to give that head a quick spritz of black paint? The rest of the motor looks so good, it kinda stands out.

It looks like you may have the 36mm carb, which would be stamped '010B' under the idle speed screw. I believe the '73 34mm is stamped 676B, but I could be wrong.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

Thanks for your comments, Ray. I may take you up on the advice of spraying the head to match. I agree that it does stand out.

As for the carb, I just got back to it and pulled it off tonight. It is stamped 009A / ALGI. I find very little info on those numbers online. Only one note stating that its a 34mm. I hope that this is the original carb for this bike.

As for the float valve operation - just holding the carb right-side up, it visibly operates as I believe it should. I also hooked the gas line up, and turned the petcock on. Gas flowed easily as it should. And operating the float valve with my finger did shut the flow off. I compared the float height with the specs in my 1975 Clymer manual (that came with the bike) and it seems in spec.

I also removed the boot between the carb and cylinder to inspect. Nothing unusual there. I can see the piston and top of the rod as I ease down on the kick-starter, and barely see the piston ring as it nears the bottom of the stroke. Everything looks clean and tight.

I'm still stumped.

The 009A stamp could very well be correct for the original carb. As far as I can tell, 70's Honda 2-stroke Keihin carb stamps started with 004A ('74 MT250) and ran to 0092B for the FL250 carbs. The 676B stamp I mentioned could be incorrect, or only for the very first CR250M's using a previous numbering system.

I don't know what to suggest now, except to check the spark again (ground the plug against the head to make sure the motor's grounded). If the crankcase were filled up with gas, you would smell it right away. If the carb's working and you're not even getting a pop from the motor, it's gotta be spark.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

Remove the spark plug, dribble a little gas directly into the sparkplug hole then put the plug back in and kick it over.

might sound silly mate, but is the plug wet at all? it certainly sounds like a fuel blockage somewhere as others have said if the timings out you'd still get something happ'nin.....wip the carb off and take a butchers in your intake port'' could be somethong there if its been stood a while!!
bike looks good.
I'd personally have the engine out and do a rebuild they really aren't that hard to do then you know your gonna have a pretty good bike!
cheers

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1976 Yamaha TY80 X 2, 1977 Yamaha TY250 X 2, 1976 & 1978 Honda CR125 Elsinores, 2013 Harley Davidson 48 Special.
Range Rover Vouge Black Edition, a Little Smart four two and a shed load of other shit!!

Hey guys! I'm back to work on the Elsinore - first a few updates, then my next problem...

I just got this project off of the back burner! Been several months since I've tinkered with it. But best news... I finally got it running! Embarrassing yet simple enough, the timing was off. It was firing strong, but a bit past TDC. I wouldn't have thought that alone would keep it from hitting or popping AT ALL. But sure enough, once adjusted so that the points began to open right when they should, it was ready. Second or third kick, I got a definite pop. I was so excited!

So this leads to my next mystery. The dadgum kick starter. The very next kick, it popped again and just jammed my ankle so hard on the kick. And the kick starter stayed down. Didn't return to top. If you pull it up by hand, it will stay and you can kick it thru again, but it still stays down. Kind of feels like its in a bind a little. So I took the R crank case cover off. Coiled up starter spring? Pawl? Nah. They are both fine. Everything (to me) looked super clean and in tack. I just figured it was a fluke deal and put everything back and cover back on. And it seemed right. With spark plug out, it pushed through correctly and returned just like it should. Plug back in, under compression, still good. So I stand up and kick again, and BAM! Same thing. It popped, jammed my foot, and kick starter stayed down again. So I took cover back off, and still nothing stood out. I took that starter spring out, looked at it, put it all back together again, and again it seemed ready. This time I decided to pull it off with the golf cart in the yard. And for the first time since (I believe) 1975, this jewel was running. Sounds like a beast. But it was dark so after a first gear slow loop around yard I rolled it in. An hour later, I had to go back out there and just LOOK AT IT again. And hey, might as well, give it a kick to see if she'll fire back up. But oh no... POP, JAM, ouch, kick starter does it again. No return and a little bind.

WHAT AM I MISSING?!? Looking at a schematic, I realize I didn't inspect the C shaped 'pawl spring' while I was in there. Could it be messed up and causing this? Is there something else I should check?

Thanks guys!!
Doug

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'74 CR250M

any updates DougMX726 ? is she runnin??

Alright guys. Time for an update. This baby is DONE!

Re: my kick starter issue: I searched thru some old posts here on the forum and noticed someone with a similar problem - and their issue was that the alignment pins were bent or tweaked. The next time I pulled the side over off - not only was my left pin a bit bent, the right one was completely missing! Honestly, I can't say if I dropped it out the first time I took the side cover off and kicked it somewhere across the shop floor OR if it wasn't there to begin with. The original owner might have had the same problem back in the mid 70's and made the mistake himself. What ever the case, I replaced them with some cold roll steel of identical o.d.'s, cut, beveled, and sanded to fit. This gave them much more strength and still had a large enough i.d. for the screws to pass thru. It kicks flawlessly with no jams.

So I finally rode it some in the daylight yesterday and this thing is a beast. Sure, I guess I'm a youngster at 33. I grew up on CR250's of the mid 90's. Owned a 93 and 96 model. This Elsinore just flat out hauls. I love it. Can't imagine anyone ever holding on to one for 30 minutes plus 2 laps! But I'm not planning on much more than it being a collection piece. Knowing it cranks, runs great, and shifts all the way thru is very satisfying. I can't decide if I will keep fresh premix in it and fire it up periodically, or just drain tank / carb and detail it for display. Selling it is not on my list. It's just too original to me.

A noted THANKS to you guys for lending some advice here on this forum.

Peace & Wheelies,
Doug

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'74 CR250M