Vintage Dirt Bike Q & A

Finally after 4 rounds of heating and freezing I got the carb apart... only to find it was WAAAAAY worse than the other one



after a little cleaning (obviously more is needed)




I'll probably swap a few non jet parts from the other carb and sell off the excess parts

does anyone know where to get the jet seat steel plate thing?

would epoxy (jb weld?) work t hold the brass plate to the aluminum body? the screws rusted off in the body and will be SUPER hard to remove

Before you spend any more money on the bike, I should tell you that replacing the kickstarter spring is a HUGE job, and even then you'd have to replace it with another used one, since NOS springs are almost impossible to find. You can remove the kickstarter idler gear to disable the kickstarter, but you may still have broken spring bits loose inside the gearbox.

If you're going to move ahead with repairs ...

That carb has one of the worst looking float bowls I've ever seen. I think it's unlikely that a carb with a completely rusted-away baffle plate will ever work well.

You probably won't be interested in doing it, but I would strongly suggest contacting the seller and requesting a refund. You paid top dollar for that carb, and in my opinion it's basically junk.

I've done business several times with the guy you bought it from, and he seems to be a reputable eBayer. I think it would be worth a try to return it, especially since you have photos of what it initially looked like. I wouldn't be too concerned about his return policy specified in the listing, this is kind of a special case.

Do you have any pics of the the carb that was on the bike? I'm interested to see if it's the MT250/MR175 unit. If so, there's a NOS throttle slide for this carb listed on eBay right now:

http://cgi.ebay.com/ebaymotors/MR175-MR ... 3a4793b244

... and Keyster makes a carb kit with the needle, jets, float valve, etc.:

http://cgi.ebay.com/ebaymotors/HONDA-CR ... 5888aa6657

Ray

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

look at my pictures AGAIN

I took the parts from the 250/175 carb and put them into the 125 carb save the jets as I bet they are slightly different.

I have a baffle plate unless this is the steel plate that goes around the main jet, I have that, but it's almost rusted out. My plan is to recondition it with jb weld if that's fuel proof

Honestly I havent seen ANYTHING ELSE I could use for this low of a price and even inf I bought that throttle slide I'd still need a needle, spring, cap, and cable adjuster...

Basically I just want to know HOW to re attach the baffle plate when the screws rotted the heads off

ALSO

I have a spare kick starter for a XL185S! that should have the same return spring, OR I bet the spring just came unseated or something stupid as everything else in the gear box seems good

the carb that was on the bike IS IDENTICAL only it has larger ports

I got some parts in today and I have a vast number of updates...

but here's the immediate worry

I got in a kickstand today, but my kickstand mount has broken off the frame (apparently I never had it)

can anyone take a picture of a MT kickstand mount so I can fabricate one? I think th 250 and 125 were the same and the CR series might be similar too

I also got a seat for $10 in Excellent shape, but the lockable latch is missing, so pictures of that would be good too

so I think I tracked down my electrical problem, I think my condenser is grounding out because I get continuity across it. As far as I know you're not supposed to get continuity across a capacitor, capacitors SEPARATE CHARGES.

so, anyone else ever get continuity from the input wire for the condenser to ground? I unfortunately dont have a way of measuring capacitance, the old trick we used to do in college eludes me (google time I suppose)

HALP!

The kickstands on these were a joke mine broke too I put the bike on its stand and turned around just in time to watch it slowly bend then snap right off. I have a spare frame with a good mount and will get you a picture as soon as I can. I also think jb weld is only fuel resistant not fuel proof but I dont know for sure.

Hey electrohacker, I have a MT carb sitting somewhere in a box somewhere in my shed. Not too bad of shape. Send me an address and I'll mail it to you here in the next couple of weeks after I find it. I stole the air mixture screw and spring out of it, but I think the rest is all there.

woosh,

I just used JB Weld on an intake manifold and was curious about the gasoline resistance too, and I found this at the J-B Weld Web site (http://jbweld.net/index.php):

"It's strong as steel and impervious to water, gasoline, chemicals, and acids."

The data sheets for both the resin and hardener indicate they're incompatible with "strong acids, alkalis, and oxidizers", but that's it.

Ray

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

I actually got the seller of the kick stand and seat to get me pictures with a tape measure in frame of the mount and he sent me the seat latch (very nice seller)

my plan is to weld two pieces of 1/8" plate to the frame, one bending one way around the tube the other bending the other way then plug an edge welding the two plates together. Then I'm going to tack on two nuts and make a second piece that will bolt on which will bolt to the kick stand. This will allow me to fabricate it without it being on the frame an if I ever wanted to build a new one it would be easy to change.

trying to get a clutch now (I over torqued an broke a part). turns out a 76 clutch has a different diameter hole for the main shaft... so I have to return the one I bought an get another and sell off the extra bits

bike's almost ready to run, I have the carb cleaned, the wireing has been gone through, 99% of the controls are in place (still need a front brake lever and mirrors)

hopefully once the clutch comes in I'll have a running bike

I need to know what thread the flywheel is, I need a puller

updated pictures







today's big hurtle SPARK

I need a flywheel puller, anyone know the thread? or maybe where to buy one?

prolly gonna need to put pipe back on too to run right....! Looks good--nice to see someone else who is obsessed with making old stuff go again--

My wife calls me "The St. Jude of Mechanical Objects"....for you who are non-catholics or don't kow the saints that well, St. Jude is the patron saint of lost causes......

are there any tricks to making the oil injector pump pick up the oil? I did the check valve trick mentioned in the service manual and it had oil flowing just fine, but then I couldnt get it to pump.

FYI the bike wasnt running, I pulled the spark plug, put it in gear, and walked it around with the throttle at half open (also from the service manual)

maybe I cant walk it fast enough and it'll just have to wait?

I suppose I could put the holding bolt back in and run mixed gas to test the pump after I fix the spark