I bought an 80’s Dr125 that didn’t start. Got it to the point that a new carb was in order. Finally got the correct one, a brand new Kehin.
If I mist the throat with starting fluid I can strategically and carefully get it to run (off choke).
A direct shot of starting will stall it. With a careful light mist I can keep it going.
When it’s “idling” on the starting fluid, it sounds like it’s running great.
On gas it won’t start. I can get it to make promising noises but if you even breathe on the throttle while kicking, those promising sounds go away.
I really want to impress my son... what’s my next move?
In reply to ebonyandivory :
Adjust throttle to make sure it's closing all the way? Some carb/engine combos really, really hate any throttle when starting.
In reply to ¯\_(ツ)_/¯ :
With the (also new) throttle slide valve, looking into the carb on the air filter side, with hands off throttle, fully closed looks exactly like this:
Make sure there's no vacuum leak going to the slide. Makes sure there's gas going into the float bowl. Make sure the float isn't stuck. Make sure the jets (and float valve) aren't clogged up with crud from the fuel line or gas tank. Is there an accelerator pump? If so, is it squirting?
In reply to Dr. Hess :
The carb is fresh out of the box so I know it’s not crud in the passages. I had filled the bowl with new gas. The carb has two barbs that look like vacuum but was “told” they’re not.
Its a simple 26mm Kehin carb, no accelerator pump.
With ZERO throttle and with gas supply, kicking it over sounds and feels promising. But like I said, even the slightest throttle input makes it lose that promising sound (and feel).
What would cause the bike to start on a MIST of fluid while a straight shot seems to drown it?
A new carb can be plugged almost instantly from a bad gas line.
When you blow into the barbs that are "not a vacuum", what happens? One should be an drain for if the float bowl is too high, what the pink hose in your pic is for. The other should probably be a vacuum. That one is capped off, right? If you take that drain off the bottom, gas comes out, right?
Weak spark can cause that type of problem.
The ether lights off easier, so it may be making an ignition problem look like a fuel issue.
I’d do a compression check, new plug, check the needle position in the slide, and confirm the right size jets are in the carb for that engine.
Do you have a picture that shows the additional nipples on the carb?
What did you do with them? Capped or open?
How did you confirm they weren’t vacuum or vent?
Are you installing the air cleaner before trying to kick it over without ether?
ebonyandivory said:
In reply to Dr. Hess :
The carb is fresh out of the box so I know it’s not crud in the passages. I had filled the bowl with new gas. The carb has two barbs that look like vacuum but was “told” they’re not.
Its a simple 26mm Kehin carb, no accelerator pump.
Those should be float bowl overflows. I have had multiple Mikunis with janky float bowl levels straight out of the box, and one with some aluminum drill swarf under the float needle (that was a fun one to diagnose).
Unfortunately, just because it's brand new, doesn't mean it's "right".
How fresh is the plug? The old Honda XL250 I am working on right now would pop and blubber But never light off, even though it looked like it had a decent spark. A fresh plug and it started and idled on the first kick.
Old motorcycles are incredibly simple things, sometimes they're just a little recalcitrant to wake up.
That carb above is not identical to mine, just used to show what the slide valve looks like with throttle closed. Below pictures are my actual carb.
On the side with the idle screw etc., there’s a screw used to drain the bowl (red arrow) which does drain from the opposite side of the carb at the bottom. It’s the lowest one pictured. Is that a vacuum port (yellow arrow) that needs to be blocked off at the 1:00 position?
Here’s the other side (obviously with fuel hose disconnected): is that a vacuum port that needs to be blocked off? Both seem too high to be overflow for the bowl.
Maybe BOTH those ports need to be blocked off?
Edit: WAIT, IS THIS A DAMNED TWO-STROKE CARB???? It can’t be, riiiiiiigggghhhttt? No, I know it can’t be possible. I’m not that stupid.
Yellow arrow certainly looks like a vacuum port. Plug it and try again. Port on the other side could be the float bowl vent, so I would try to confirm that. I also second Ethnic's comment about possible manufacture swarf or incorrect setting. This carb has never worked on anything (yet).
Any chance those ports are vacuum signals that tie multiple carbs together to smooth out idle on multi cylinder configurations?
In reply to oldopelguy :
Very doubtful. This carb fits many engines, none of them have a multiple carb set up (like my Suzuki GS).
TurnerX19 said:
Yellow arrow certainly looks like a vacuum port. Plug it and try again. Port on the other side could be the float bowl vent, so I would try to confirm that. I also second Ethnic's comment about possible manufacture swarf or incorrect setting. This carb has never worked on anything (yet).
First I’ll plug that yellow-arrow port and see what happens. If nothing, I’ll take the carb apart and see if I can find passages blocked.
How can I determine if that other port is vacuum or a vent?
Blow low pressure air through it and see if it comes out in the venturi.
I remain that those are overflows, but I suppose "Float Bowl Vent" would also be an apt description. They seem high right now, but it will be a different story when the bike is laying on it's side.
The only difference between a "2 Stroke carb" and a "4 stroke carb" (at least in the Mikuni world) should be the needle jet; bleed type vs. primary type. Obviously, jetting requirements are going to differ greatly, but that's the view from 30,000 feet. They'll both run on either type, though.
In reply to Ethnic Food-Wrap Aficionado :
Thank you.
I did block off the one that seemed to be a vacuum... no change. The other side nipple did blow air through the venturi when I blew air into it. I’ll try it in the “yellow arrow” side shortly.
I have it hooked to real gas now. There’s a shot that it’s weak spark that can ignite ether but not the gasoline.
Ill have to look into replacing a component or two
Can you (should you) test the coil? They’re only ~$15 but if it’s testable with an ohmmeter...
The more I think about how well it ran on a mist of starting fluid and sounds promising on gas, I’m thinking of pursuing the theory mentioned above, that says weak spark (plug is new).
Does this sound reasonable considering the nice running on one highly flammable substance but not quite igniting the gasoline?
ps: the pipe gets hot when I go nuts kicking it on gas so it’s doing something.
Edit: I’m gonna do a primary and secondary test on the coil using my multimeter. Thanks YouTube
So, primary side testing is usually done after you unplug the two-wire lead off the coil and probe the plug. This coil is of course different than the video and has leads off both ends of the coil. When putting the multimeter on either side, I get 0.3 ohms where I believe you’re supposed to get between 3.-5. ohms. I have no clue if this is right and the coil is bad. Keep in mind this bike is kick only with no battery if that matters.
Furthermore, you test the secondary side with one lead from the coil and the other into the spark plug boot in this case reads NOTHING where it’s supposed to read close to 14,000 ohms.
Can anyone tell me if this coil, for a quad with the same motor can be used? It has a blade connector where the factory one just has two mounting lugs with leads screwed into them.
Would I just solder in a female blade on that one end?
If it needs a coil use something like this. My RD350 runs much better with these, they are cheaper and available in damn near every parts shop. You can just zip tie it on or it is easy to make a simple sheet metal bracket
In reply to pilotbraden :
Hmmmm, interesting. I can pick one up for under $25...
