HELP... Moped dies when throttle is opened up

thomasdepersia /

Hey ya'll,

I have a < > model moped that I've owned for several years.

First I must tell you it has been out of commission for almost 6 years.

Today I began to work on the bike and got pretty far. I removed the gas tank, cleaned the insides very well and put fresh gasoline properly mixed with 2 cycle oil into it. I flushed out the tank line to the carb with fresh gas.

I took the carb off the intake - sprayed the fuel intake filter out with cleaner spray, sprayed some cleaner through the main body, opened the throttle up and down and sprayed that intake. Everything already seamed asthetically clean from all ports however, but I sprayed them down a little anyway. The choke was a bit stuck at first, but snapped on and off good with a small shot of cleaner.

I replaced the spark plug with a new Bosch according to the original model. I removed a small amount of surface rust on the rubber plug connection.

I took the muffler off the bottom of the motor - that was fine. There was some crud at the front but I took it off and air was flowing through it fine anyways.

With some fresh air in the tires, I got on and attempted to start it up. I took a few tries down a small hill, but didn't start. I looked at the carb and there is one screw on the right side of the body with a spring under it - it was turned all the ways turned in. Reading from some information off this website I opened the screw by 2 full turns. The bike started right up after that.

My only problem is this - the power is way under. I do not know if it has to do with the carb, motor, spark, or whatever.

The bike starts right up with a few quick pedals - but when I rev it high it seems to drown out. When I go up a small hill it will drown right out when I hit the throttle. When I hit the choke, it runs strong right up to the point where the throttle is maxed and releases it - then it'll start to drown out on a flat straight-away. If the choke is on, it runs strong. On a straight away I open the throttle all the way, which releases the choke and it dies.

Any ideas?

Thanks

Re: HELP... Moped dies when throttle is opened up

thomasdepersia /
OP

The model is a Cimatti by the way.

Re: HELP... Moped dies when throttle is opened up

thomasdepersia /
OP

Ok one more thing - opened the new plug and it was a little white on the top, and black oily fluid around the outside thread and head. Any ideas now?

Re: HELP... Moped dies when throttle is opened up

Check the carb for a choke and see if you can regulate the air coming in. Sounds like you may not be getting the right mixture of air and gas. Also check the air filter (if there is one) to make sure it is not blocked.

Re: HELP... Moped dies when throttle is opened up

thomasdepersia /
OP

I cleaned the air filter, so i know that it is not the air filter causing the problem.

However, I do think it has something to do with this one screw on the carb, which i've turned and adjusted, but haven't found the right mixture? Theres only one main screw on the carb that looks adjustable, i believe this is the screw that regulates the air coming in. I've adjusted this to different # of turns, but still the moped stalls sometimes.

Please Help, thanks

Re: HELP... Moped dies when throttle is opened up

the one screw that is adjustable is prolly the idle screw........sounds like to me its either a jetting problem or u have an air leak.......take starting fluid and spray it aorund the card while the bike is runing and if the motor revs up then u have an air leak also make sure air cleaner is hooked up properly....

BlAiR

Re: HELP... Moped dies when throttle is opened up

check the main jet for blockage.Jim

Re: HELP... Moped dies when throttle is opened up

Don Pflueger /

you need to remove the carb, disassemble it, soak it in carb cleaner, poke a fine piece of wire thru every hole you can find in its body and all its parts, then reassemble it, start the bike up and adjust the mixture screw correctly. by the way, what bike/engine is this?

Re: HELP... Moped dies when throttle is opened up

Don Pflueger /

its definetly not your air filter. you mentioned it runs better with the choke closed and that your plug is white. that means it is too lean. the carb or something in the fuel system is partially plugged up, or you have an air leak. i'm betting your carb is dirty inside.

Re: HELP... Moped dies when throttle is opened up

Exactly don... If a bike has been sitting for a long time there are certain things that you always do.... Check tires for crackage, clean the carb, decoke the piston top, cylinder head and exhaust port, drain tank and check for rust, then flush it out, new gas and spark plug, change the tranny oil...

Re: HELP... Moped dies when throttle is opened up

Oh and check the points gap and clean them...

Re: HELP... Moped dies when throttle is opened up

This problem can easily be fixed. If you listen to Morrissey while fixing your moped everything will work fine. I know it may sound funny, but it really works, i swear. Try it out

Re: HELP... Moped dies when throttle is opened up

thomasdepersia /
OP

Ok guys thanks for all the replies so far...

I tried starting my moped up this morning, and it started real quick. I put the choke down, and the moped accelerated fast.. I took it on the street and was going like 30 mph until i slowed down to take a turn and it stalled.. I noticed the choke lever was up by this time.

I have some questions about a few of the replies, but will first tell you what ive done to the bike to get it running:

-I cleaned out the gas tank with a phosphoric acid mixture, and flushed it out, then filled it up with new gas/oil mixture.

-I took the carb apart and sprayed it with a carb cleaner all throughout the insides... (i didn't poke holes with a paper clip or clean the main jet*)

-I installed a new spark plug (but i noticed a white residue on the spark plug after running the moped for a while)

Questions:

-How do I decoke the piston top, cylinder head and exhaust port? (in response to crisis)

-How do i check the points gap and clean them? (in response to crisis)

-I've located one adjustable screw on the carb, that if i adjust while the moped is running, it seems to idle the same, but give a different response to the throttle. (this is either the gas/air ratio screw or the idler screw, im not sure which)

Im thinking its the carb and im gonna take it apart today and clean the main jet and try to poke holes with a paper clip...

Re: HELP... Moped dies when throttle is opened up

Cole Todorovich /

its your crank seals they are going bad. as you give it more throttle more air leaks and possibly gas into the bottom end. and you lose compression and bog down. this happens alot with 2 strokes that have been sitting. drain your gear oil and see if it has gas in it.

lanesplitters

Re: HELP... Moped dies when throttle is opened up

If it starts and is running your points are probably cool, but to check the points gap or clean the points you remove the magneto cover. The points are under the magneto. When the piston is at top dead center the points should be all the way open at whatever the points gap should be for that engine... I don't know off the top of my head what it is for your minarelli. To clean the points you bring the piston all the way back so that the points are closed. then pry them open and place a piece of 600 grit sand paper folded in half in there. Then let the points close on it. Then drag it out. Do this like 10 times... This is usually done only when you don't have good spark or no spark, so it's probably not going to fix your problem... To decoke the piston crown, head and exhaust port basically means that you scrape the carbon that is built up on the piston crown, head and inside the exhaust port off. I usually use a thin flat head screw driver. Just be careful not to gouge it or make any deep scrapes on the piston crown or head, since they are alluminum... If there is a screw on there besides your throttle screw, it's usually an air mixture screw, which will only effect your throttle response at idle. It basically controls the air/fuel mixture at idle... To me it sounds like you need to really clean your carb and make sure there is nothing in the main jet...

Re: HELP... Moped dies when throttle is opened up

You can't just assume it's his crank side seal, just because it's running shitty. 99.9 percent of the time it's a dirty carb or weak spark... But yeah, if there is gas in your tranny, your crank side seal has gone south.

Re: HELP... Moped dies when throttle is opened up

Don Pflueger /

most often when a crankseal goes bad an engine cannot maintain idle because it cannot hold the vacuum or the pressure needed for proper fuel/air flow.

Re: HELP... Moped dies when throttle is opened up

I'm actually having this problem with my Vespa scooter... I have to replace my clutch side seal this weekend. One big symptom that I have notices is that it idles high when it's warm and makes no power... Plus the obvious gas in my gear box...

Re: HELP... Moped dies when throttle is opened up

and it's a bitch to start...

Re: HELP... Moped dies when throttle is opened up

Check the reed valve and try a different jet.

Re: HELP... Moped dies when throttle is opened up

My moped had a rusty gas tank and keep cloging up my carb on my old Vespa other then that it works like new. :)

Re: HELP... Moped dies when throttle is opened up

Having similar issue with 1999 Tomos Classic. Cleaned carb and jet, emptied fuel and replaced with proper fuel/oil mixture. From the responses on this forum, my next move should be to:

A. Check and replace crank seal?

or

B. Check points and timing, adjust and clean points, etc.

Thank you,

KB

Re: HELP... Moped dies when throttle is opened up

Restart your process by using the Repair Forum and the very first thread—that’s about the wiki and Fred’s guide. You’ll frustrate yourself and others as long as any important steps (variables) are left out or checks are not performed. Get to know your engine and a bit of detail, helps a ton to know you have a Minarelli V1 with a Dellorto SHA carburetor (right?). That helps you drill more deeply into the wiki for more intensive troubleshooting. Rule out basics like the seal at your intake by just replacing the shim and o-ring type gasket. Totally clean carb plus those items could eliminate important variables. The time you spend is worth it for your peace of mind, but also gets you better advice here. Hang in there and post again when you make some progress.

Re: HELP... Moped dies when throttle is opened up

lol

« Go to Topics — end of thread

Want to post in this forum? We'd love to have you join the discussion, but first:

Login or Create Account