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btcn 07-27-2010 10:07 AM

Carburetor problem
My new engine works well and has a ton of compression, but I don't think the carburetor is good. I am using my old carburetor from the old engine, as the new engine did not include a carburetor. The engine will only start with the intake hole where the air filter pipe goes blocked completely. It will not suck gas through the tube without this blocked with a hand. If you put the air filter tube on, it will not even really try to start. But when you block it, it will fire up and run great, and gas comes out of the hole and through the tube. I was thinking maybe it was a problem with the vacuum system or the carb was bad. I have cleaned it and everything, but it did not help at all. It seams that the carb does not want to pull gas through the fuel tube at all with just the air filter tube on. I think it is because maybe the carb is bad or has a problem.

I would appreciate any suggestions on the carb or vaccume system.

tortoise2 07-27-2010 11:38 AM


Originally Posted by btcn
I would appreciate any suggestions

For those lacking telepathic abilities, more CONTEXT might be helpful . . such as posting a carb model or application reference.

btcn 07-27-2010 01:20 PM

The carb is for my Honda Elite 150 scooter. I just replaced the old engine, which stopped running due to compression problems, and the new engine is not running due to carb problems as far as I know. I guess I just forgot to mention that.:nod

tortoise2 07-27-2010 02:29 PM

Have you reviewed previous related discussions . . example?

btcn 07-28-2010 07:13 PM

Yes, I reviewed a couple of them, but I was just wandering what would cause the engine to run so well with the air intake blocked completely. It will not even run at all with the tinniest open space. I will look at more of the carburetor threads and see if anyone had a similar problem.

c_mccann 07-29-2010 08:05 AM

You say new engine, is it rebuilt fully, or a used one that is in running condition? Have you checked the compression? It is the compression that 'sucks' the gas vapors into the combustion chamber. Covering the intake, or 'choking' is the sign of a plugged carb, but you have cleaned it completely. I'd almost wager a look at the valve train, do you have access to an unvalved compression meter to do a leakdown test?

MODNROD 07-29-2010 09:12 AM

Try as hard as I might, I always think of cleanliness when doing engine swaps AFTER I've put the thing in.

It usually occurs to me when I realise that tiny bit of dust that got into the carb while it was sitting in the frame/on the bench/under the carport for 2 weeks waiting for the new engine, has now migrated to the idle air bleed at the inlet side of the carb, so the bastard won't idle........oh yeah, and it runs crap, because ANOTHER tiny bit of dust has also blocked the mains air bleed too, dammit. :rofl

btcn 07-29-2010 05:54 PM

Thanks for the ideas with the carburetor. It probably is something like that. But another thing I noticed is that the piston in the intake is down, and doesn't appear to work. The owner's manuel suggests this as one of the problems for not starting in the owner's manuel. But I decided the best thing would be to get a brand new carburetor. I found one on ebay, and I decided to buy it and see if it would work. It is only like $60 including shipping.

And for the engine, it is a used one, but it has almost no miles on it, looks great and I am pretty sure it has good compression. I was thinking it was possibly even a valve problem, like maybe they were not adjusted correctly, but the way it starts plugged and with carb cleaner spray, it has to be a carb problem.

Another thing I noticed is that the breather tube going from the back of the air filter to the transmission was not in quite right, and I can not get it in. I do not think that this has to do with the carb problem, but I would like to now what this is really for and if it is ok to run with it out. I appreciate the help so far.

MODNROD 07-29-2010 06:51 PM

The breather tube is to vent the box. If you take it off, then oil mist will cover stuff, and a possibility that dust will get into ur gearbox too. Keep trying to get the hose back on (maybe just hold your tongue JUST right! :rofl ), but if all else fails use a little filter over the hole.

btcn 07-30-2010 10:05 AM

Thanks for the information on the breather tube MODNROD:thumbup . I will see if I can get it back in today, maybe with a small piece of metal in the tube so that it doesn't collapse. As for the carb, I cleaned it even better, and put it back in. Then I redid the fuel air vacuum tubes and all of the other tubes and it finally fired up and ran well! It was probably the vacuum system, as it did not appear to be pumping fuel to the carb right, and it finally started working. Now I just need to get the radiator hose tightened better, as it leaks a little when I run the engine, and fix the breather tube, and it should be good to go. I appreciate all of the help.

btcn 07-31-2010 12:18 PM

I got my Elite 150 running finially! It runs and idels great! I got the breather tube in after about 45 miniutes of screwing with it, and I got all of the tubes and conections right. It runs smooth and rides great. I can get it to 60 mph with ease, and I might even get a little more out of it, as I have not completely toped it out yet. The mid to high range acceleration seems even better than the old motor. I will probably just do a couple more things, and it will be in peferct condition. :D

Dabears 07-31-2010 01:14 PM

Congrats to you. Always nice to get something back on the road after some significant work. Sounds like it moves out pretty well!

c_mccann 08-01-2010 12:54 PM

Nice!!! Congrats! Enjoy riding your revamped beast.!

btcn 08-01-2010 02:37 PM

Thanks. It does work quite well now! The engine is rock solid and has plenty of compression, and the transmission is smooth. I replaced the transmission/gear reduction oil with brand new oil, and lubercated it and got all of the parts working great. I just fixed the starter switch as it was not turning the headlight on, but now it all works great! It is solid at 50 mph and will even go over 60 mph, is very smooth and quiet, and will run 45 mph up even the steepest hills. Hopefully it will work many more miles before I need to overhaul it again!:lol3

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