Jonway 54B rough running only when hot outside By Saber (Read 512 times)

[Saber]

Looking to the brain trust on this one. All winter long here in the south the bike ran with little to no issue. The last couple of days it has reach passed 80 degrees outside and the bike is giving me issues. This morning it was a cool 50 and I made the 7 mile trek to work with no issues. Today on the way home around the 5 mile mark the bike began to stud-er. Mostly after coming off the throttle then coming back on while traveling around 35mph. I was able to reproduce the issue while on that stand and made a video.

In the video I gave it about 1/4 to half 1/2 throttle and kept it there throughout the whole video. It would rise to 4000rpm on then down to 3000 and back up all on its own in the video while keeping my hand still on the throttle.

Any thoughts on what is making it bog / studder like this.

[Saber]

Well I upped the main jet from 115 to a 117.5 and my pilot jet from a 38 to a 40. I still have the issue but it occurs less frequently. So I went to a 120 jet and it just didn't run right. Back to the 117.5 jet and started moving the needle from its upper most setting with a shim down to the middle.
Still has the issue but not as bad. If anyone has any incite I would appreciate it. I would hate to be just bandaging this issue instead of doing it the right way.

[JR]

Vacuum leak and/or valves need adjusting. The linhai does weird things when especially the exhaust valve is too tight.

JR

[Saber]

May 9, 2014 6:13:53 GMT -6 JR said:

Vacuum leak and/or valves need adjusting. The linhai does weird things when especially the exhaust valve is too tight.

JR

Thanks for the reply, here are a few more things I have done. I did the valves as my first step, please note this is a 172mm Honda Clone,

Also I have removed almost all vacuum from the system now so I am down to just one line for the carb.
Last year I installed a UNI Dual Layer foam filter after my air box and everything related to that cracked and fell apart. I have dropped all emission equipment from the bike freeing about 10lbs off the thing.
I was averaging around 65 to 70 mpg during the winter but now that warm spring is here I am garaged until I get this figured out.

In my process to cure this current issue, I have gotten rid of the vacuum pump and I am now using an electric pump for fuel. At first I thought it was fuel starvation by the sound but its so hard to diagnose sounds through a helmet. I am honestly struggling with the is this a lean condition or a rich condition, A plug check shows that after 1000miles in the bike my plug looks the same as it did out of the box???

[JR]

Sorry my bad thought it was the linhai. First of all the things you did as far as electric fuel pump install and removing the emissions system was all a waste of time unless there was vacuum leaks. Proven fact the engines run no better with the systems disconnected. A good vacuum fuel pump works just as good as a electric one if all lines are good and not leaking.

Now since you mentioned you have added a filter from winter time to summer time riding conditions/weather are a totally different ball game, cold air runs better than hot/humid air. Now you've got to fine tune the air/fuel ratio to work correctly. I'll let Alley take over form here, he's the carb man.

I don't see any mention of cleaning the carb especially the high speed jet orfice?

JR

[Saber]

May 12, 2014 5:44:17 GMT -6 JR said:

Sorry my bad thought it was the linhai. First of all the things you did as far as electric fuel pump install and removing the emissions system was all a waste of time unless there was vacuum leaks. Proven fact the engines run no better with the systems disconnected. A good vacuum fuel pump works just as good as a electric one if all lines are good and not leaking.

Now since you mentioned you have added a filter from winter time to summer time riding conditions/weather are a totally different ball game, cold air runs better than hot/humid air. Now you've got to fine tune the air/fuel ratio to work correctly. I'll let Alley take over form here, he's the carb man.

I don't see any mention of cleaning the carb especially the high speed jet orfice?

JR

Yeah I wish I didn't have to go the route of gutting the system out but it was spend $200 replacing all the broken, busted, cracked parts or dump it and spend $20 on a Uni and some new lines. But that was last year and 1000 miles ago.
Anywhooo,
The carb only take about 5 minutes to pull out now I didn't do a complete tear down cleaning but I did pull it and spray it down while doing the re jet. I'm sure if anyone out there has done this to there 54b's they might be able to give me a starting point on the jetting.
This thing is a little more fickle then my 150cc was.

[Saber]

Thanks to another poster that was having the same issue as me with a similar set up it turns out replacing the carb was the fix. I rebuilt my original last year while the bike was having other issues but the way it was acting this go around was really throwing me.