Stalls when you wrap the throttle By Saber (Read 1,602 times)

[Saber]

I've got a Jonway 54b, Honda Clone, about 3 years ago I dropped the emissions and air intake and went with a Uni 2 stage and bike ran great with a simple raise of the needle and up jet from the stock 105 to 120

Starting half way though last year I have struggled with this issue and I know im missing something,

When stopped at a light if I go from zero to 1/4 or to 1/2 throttle the bike will die as if I just shut it off. If I ease it she will start slow might hick up but will then reach full speed no issues. Bike idles great and runs well at WOT.

What I've done
Valves, Checked checked again and doubled checked by a friend
Replaced the carb
Changed main jets installed 115,120,125,130,135
Changed pilot jet installed 30,32,35,37,38,40
raised the needle shimmed the needle lowered the needle.
Finally I retrofitted a pumper carb (the one you would find a Yamaha clone) on the thing thinking my problem is leaning out in the mid range and this would help. Bike ideals strong and runs strong as long as I don't wrap the throttle from a stop.

HELP!!

[JR]

When you say you've done the valves, what do you have them set at?

JR

[alleyoop]

If it picks up when giving throttle slow but falls on its face when you open the throttle quick that means it is getting to much AIR and not enough fuel at that point.

Follow this procedure to adjust your carb: And take your time 1/4 to much one way or the other makes a big difference in performance.
Alleyoop

thescooterprofessor.proboards.com/thread/3001/4-stroke-carb-tuning

[Saber]

JR, its a honda clone so I followed the procedure from this site. I wish there was a way to check with a feeler gauge. My ears aren't that great that's why I had a friend listen to and check them as well.

alleyoop, I've tried that but this is the reason why I am asking. Ive had this bike for several years now and I am pretty mechanically inclined so I just wanted to be sure I am still on the right track and not barking up the wrong tree. So these symptoms are air fuel related and not something else?

Its just odd to me that this bike ran so well for almost 2 seasons with the 2 stage uni and a 120 main and a 38 pilot and then it just started doing this. Thats why I swapped the carb at first thinking it would be something as simple as that but when it had the same issues with the new carb I started changing jets, and adjusting the needle to the point of shimming it. Nothing would solve this mid range cut out. All the the changes listed above were done one at a time over a 5 month period. I would always wait for the bike to completely warm up for at least 20 minutes before any adjusting or road trial.

[fflintstone]

Question--is that jonway a 54 B? if so ,you gonna need to adjust the valves with a feeler gauge with the engine set exactly on the timing marks to assure the cylinder is top dead center--probably need to do that with any engine--check our tutorial on setting the timing marks ---setting by ear is not the best way on this scoot--good luck--fflintstone

[Saber]

Jan 31, 2015 10:09:40 GMT -6 fflintstone said:

Question--is that jonway a 54 B? if so ,you gonna need to adjust the valves with a feeler gauge with the engine set exactly on the timing marks to assure the cylinder is top dead center--probably need to do that with any engine--check our tutorial on setting the timing marks ---setting by ear is not the best way on this scoot--good luck--fflintstone

I wish,
No its the honda clone type that you adjust while the engine is running.

[alleyoop]

So it is the 244cc Vertical motor with the valve adjustments on the outside of the valve cover. The adjusters both should be near the center and they usually will vary 1 or 2 notchs off from the last mark due to wear.
So if one is way off to one side or the other then that valve is set wrong.

[Saber]

Well I tried to upload a picture of where my valves are set but it said the forum has exceeded its upload limit. My pic is only 216kbs.
The picture would have shown where I marked the original mark with a sharpie and the new location. Its about half a mark from original on both intake and exhaust.

[JR]

Feb 1, 2015 5:32:30 GMT -6 Saber said:

Well I tried to upload a picture of where my valves are set but it said the forum has exceeded its upload limit. My pic is only 216kbs.
The picture would have shown where I marked the original mark with a sharpie and the new location. Its about half a mark from original on both intake and exhaust.

You can put your pictures on a hosting site, (photobucket ex) and then put them here.

[JR]

Feb 1, 2015 5:32:30 GMT -6 Saber said:

Well I tried to upload a picture of where my valves are set but it said the forum has exceeded its upload limit. My pic is only 216kbs.
The picture would have shown where I marked the original mark with a sharpie and the new location. Its about half a mark from original on both intake and exhaust.

While one can get the valves close with the engine not running Honda came out a long time ago stating that  best/proper way to set the valves on the Helix (your engine is a copy) is with it warm and running as in this video:

thescooterprofessor.proboards.com/thread/373/valve-adjustment-helix-cfmoto-engine

[ellpee]

BTW, that upload thing is when you try to upload direct to the forum -- can be worked around by using one of the web-hosted picture sharing sites. Don't have a link immediately available, but if you search the forum for "upload" chances are you'll find one. Requires setting up a free "account" on whichever you choose, something I intrinsically dislike, but it works and I've had no issues with it.

Hey, just noted there's a link to Photobucket at the bottom of the page. That's one of them.

[alleyoop]

Since it was running good for a couple of years and now it is running LEAN all of a sudden, I think you have an AIR LEAK. So check your intake manifold for cracks and or some hoses with cracks.

If it runs good throttle up normally and does not want to die when coming to stops your valves are fine. It is all fuel delivery problem. Now if all of a sudden it got really cold out then it needs more fuel. Remember motors 60+ temps less fuel -60 more fuel.
Alleyoop

[Saber]

Feb 1, 2015 15:07:00 GMT -6 alleyoop said:

Since it was running good for a couple of years and now it is running LEAN all of a sudden, I think you have an AIR LEAK. So check your intake manifold for cracks and or some hoses with cracks.

If it runs good throttle up normally and does not want to die when coming to stops your valves are fine. It is all fuel delivery problem. Now if all of a sudden it got really cold out then it needs more fuel. Remember motors 60+ temps less fuel -60 more fuel.
Alleyoop

This issue really rares it ugly head when it's hot outside. Im thinking along the same lines as you I pulled the intake and found a fuel ready RTV and used that around where the intake meets the engine. I have also replaced all vacuum lines and tee's.

A question to go along with this is my fuel pump, it is OEM and delivers fuel just fine because I can cruise wide open for miles its just starting off thats my issue here. Anyway I am always finding about a teaspoon of fuel on the vacuum side of the pump. Is this normal or could I be pulling air and fuel from this.

[JR]

You could have a fuel pump with a cracked diaphragm, if it's OEM I would replace it with a Mikuni.

JR

[wheezy]

JR has a point. I cannot think of any circumstance in which it is good to have fuel IN your vacuum line. That teaspoon of fuel would dampen any vacuum input to the pump.