looking for carb experts! Kymco People 150 2002

[cobiecat]

Hello,

I put a compatible aftermarket carburetor on my 2002 People 150 a while back. The main problem is that the scooter won't start easily when the engine is cold (it cranks and cranks just fine), but if I do get it started it runs great; idles fine, accelerates fine, has plenty of power, no strange noises. The engine will restart very easily after being shut off as long as it hasn't been more than an hour or so and the engine is still slightly warm.

I checked the bystarter: No issues at all, there's ~12V ac to the bystarter when the engine is running, and the plunger extends/retracts several millimeters as expected.

Here's the weird thing: As an experiment I loosened the bystarter with the engine warm and running and pulled it up out of it's socket a bit - there was no change to the engine sound or rpm even though the mixture should have gotten richer. Then, with the engine still running I completely removed the bystarter - still no change to the engine sound or rpm.

I pulled the carb and found the main jet, idle jet and the enrichment jet were all perfectly clear with no clogs. Underneath the bystarter mounting plate there are 3 ports. One goes to the air intake side of the carb, and it is clear. Another goes (indirectly) to the enrichment jet - it's clear too. The third seems to go to the engine intake side of the carb, it is a relatively large passage but is totally completely blocked, almost as if the passage was never drilled through completely. That might explain why the bystarter can be removed with no affect on engine rpm or sound (the circuit isn't doing anything at all because it's blocked). I can't get a wire up the passage so assuming my diagnosis is correct I may need to drill out the brass plug to get to the passage to clear it.

Anybody have any thoughts on this? I can post some photos of the specifics if that would help.

Thanks,
Cobiecat

[Stig / Major Tom]

Good morning,  and welcome to the forum!
Certainly not an expert on carbs here, but your thinking seems sound to me. Your engine is not getting enriched for starting....and your carb does not seem to permit this, as it stands now.
Stig

[Ruffus]

Welcome here too. Not an carb expert, but maybe pics in this subject are of any help.
https://www.kymcoforum.com/index.php?action=dlattach;topic=30858.0;attach=19776

[eamartin]

Does the bystarter have a needle which extends down toward a passage where the fuel is drawn up from the float bowl?
Also, what was the reason you installed an aftermarket carb?

[cobiecat]

Thanks for the welcome, and thanks for your responses!

After finally confirming that the air/fuel mix had nowhere to exit the 3-port bystarter manifold, and determining that the relatively large passage wasn't blocked by dirt but simply wasn't connected to the manifold I decided to drill out the brass plug for the passage and drill the hole deeper so that outlet port could connect with the bystarter manifold. Instant fix! Maybe this will help someone in the future with a similar issue. Basically it was a manufacturing defect in the aftermarket carb. The original carb was totally gunked up after sitting for a few years - I stupidly tossed it even though it probably could have been saved (oh well).

The scooter now starts like new, almost instantly even. Attached (I hope) are some photos that might better explain the fix.

[john grinsel]

Get a OEM carb----they should last at least 40,000 miles until slide starts to wear.

[cobiecat]

Yes, I may go for a new OEM carb. I never seem to learn my lesson opting for the cheap stuff. It's not urgent at this point as I'm up and running.

Can you guys recommend a place that sells OEM Kymco carbs? I checked KymcoPartsOnline and they don't have the complete carb assembly in stock (at $160). The bike itself is in pretty good condition. It used to be my dad's - I think he bought it used around 2004. It currently has about 7000 miles on it.

[Ruffus]

@cobiecat,
thanks for giving this feedback.
..maybe it's just my oldfashioned thinking, that, since you found out the real source of this mishap (construction defect) are good to go on your scoot.
Just changing parts on suspicion is what (most) dealership is doing nowadays. But to find out and fix it is quite another skill level. Congrats.

[cobiecat]

Thanks Rufus. I like fixing things, and the more mysterious the problem, the harder it is to stop looking for a solution!

[JJJoseph]

My first response is always: don't drill or cut anything! On Chinese scooters (including Kymco) everything can be cleaned or adjusted. After checking that the after-market carb is the right size (hugely important), my first suggestion would be to change the pilot jet and check/clean the accelerator pump. But above all: DON'T DRILL OR CUT ANYTHING!!  Oh, and one other thing: after-market carbs are sometimes real junk.  But you didn't say if it's a brand-name like Keihin or Oko, or a no-name.

[cobiecat]

I'd generally agree with not drilling or cutting anything. In this case though, I spent a heck of a long time really digging and trying to understand how the bystarter circuit was supposed to work, and the only conclusion was that the machining was not done correctly - and I was totally overjoyed when I put the thing all back together after fixing the circuit and the scooter started extremely easily, runs nicely, and continues to start and run very well after many short and medium length trips.

Still, I wish I had saved the old OEM carb because as you say, that one could have been made to work well without any mods.

2002 Kymco People 150
1977 Honda CT-90 Trail

[Ruffus]

@cobiecat,
it's always a good feeling to find the real source of any challenge (don't want to say problem).
AND, what could have happened if you would have messed up with your aftermarked carb? Okay, a few quids gone but an experience won.
Congrats to this achievement again.