S&R motorized "bobber": running but need help w carb/ engine adjusments, please.

[fabgear]

Hi everyone,

The actual thread on my bike is in the road nike section, but not thatnive given it the first tests.today, I could use some more specific help... so here I am.

I've got the bike done essentially, other than 2 vintage style stem mirrors for the handlebars, which should be here later this week. Today was the first test start, and overall it went quite well but I do have a few questions or concerns.

I was able to start the bike right up after about five turns of the pedal, after releasing the clutch (choke open). The bike seems to have plenty of power, it really does seem to move quite well and quite strong. However, I don't know that I've ever adjusted the idle on a 2 stroke motor and I'm not sure if I have the fuel mix too heavy or not or if there's something else to address.. here's what I'm noticing:

The bike idles quite rough, and if I release the throttle it will conk out within a few moments. When you're building up from a lower speed or hang your around a lower speed, you can definitely hear the engine either choking or aspirating a little here and there and sounds like the engine is pulsating slightly.

I haven't adjusted the idler screw at all yet other than just messing with it a little bit... trying to just open it and close it some and see what happens. If I close the choke on the carburetor, which is just the stock carburetor that came with the engine, it will run really slow and will stall out itselfv. I haven't noticed any fuel leaks so far other than when I was almost out of gas finally (I only put in 1/4 tank, and mixed one pack of Opti to one gal of gas today), I noticed that that last short piece of hose running from the back of the pancake fuel filter to the carburetor was leaking some right at the brass connection to the carburetor. I read that the fitting is actually 3/16th of an inch and not 1/4", so I will get another piece of fuel line from work tomorrow (3/16") and I will just heat up the other and to expand it and slide it over the 1/4" barb of the fuel filter.


Any suggestions on where to start? I don't know if that last connection of fuel line is causing the equivalent of an air or vacuum leak and if thats causing some problems, I don't know if it's that the air filter needs to be removed or replaced with something different or if I just need to mess around with the idler screw until I find a happy medium... or maybe something else?

When I'm actually just riding it, it really moves and seems to handle quite well.... I think it's just a matter of some sort of adjustment or some sort of tweaking to get it to run really well but I could certainly use some help those that would know. It's a blast to ride right now and I'm really enjoying it even with just trying it out today for the first time. Thanks in advance...

 

[fabgear]

Alright... sometimes I can be pretty stupid. I think, looking back, I was keeping the clutch out when stopping..... sigh (it's been a while since I rode anythig with a motor). I've got to address that fuel line first, then I'll retest and see if that is what was going on and if I can then adjust the idle. Not sure about the surging/ sputtering I noticed but that could.just be the nature of these and I just don't know it, or it's just the engine breaking in still... any advice is greatly appreciated.

 

[fabgear]

Small update....

Turns out once I remembered to put the clutch in, it idles just fine. I do need to figure out exactly what is an optimal idle.... am I just looking for a smooth and consistent speed or do I need to adjust it as low as I can without it conking out? Right now, I have it set so that it is idling nice and smooth and doesn't sound like the engine is about ready to take off so I'm guessing that's probably OK?

I also adjusted the throttle inside so that the plunger opens fully now, though I did not try to adjust the needle. I'm not sure if Its running a little rich or not but I do know that the engine has not had very much use...

Took it for another ride this evening (1/2 hr) and it really picks up speed and rides nice and smooth and stops and idles really well. I just need a front brake still and I should be basically good for a few longer tests. A big thanks to the knowledge on here...definitely has helped me and given me lots to go on for mine when I get to it.

 

[crassius]

you'll find that idle and general power band will change quite a bit during the first couple hundred miles as the engine runs in - not much tuning you can do before the engine has developed full power

 

[fabgear]

Alright, the bike itself is now done for all intents and purposes. However, I'm still attempting to adjust as well as I can at this somewhat early stage of its breaking in period and could use some advice.

As of right now, the bike pedals to start. It will sometimes feel like its trying to but won't spark or catch and then if I pedal a little more then it will kick. At idle, it seems to run ok and will sit at idle fine. If I sit for more than a few seconds though (say if I was at a stop sign or something), as soon as I release the clutch and start to go, it' ll conk out and die. Then, a few feet of pedalling and I can go again.

If I run the bike and cruise, it seems to accelerate and pick up just fine, but if it drop the throttle almost or all the way down and let the bike almost coast, it feels like its sluggish and almost ready to die, and if I do that for too long, it will.

I'm wondering where I should start; is my throttle not open enough, is it open too much? Is my idle not set properly? Is my fuel mix wrong? (1 gallon Opti pack to one gallon of gas)

I've put a brand new plug in it and ran it on that lately. I haven't pulled it yet to see the color. I think the spark plug boot is crap, so I'm planning on putting a better car one on it.... maybe that will also help.

I'm eager to hear any and all suggestions.

-Jeff

 

[maniac57]

Put the needle in the second slot from the top and see if it helps.
Most engines are super rich from the box to help prevent warranty claims.
It should smooth out as it breaks-in as well.

 

[fabgear]

Put the needle in the second slot from the top and see if it helps.
Most engines are super rich from the box to help prevent warranty claims.
It should smooth out as it breaks-in as well.

Are you referring to the E clip on the throttle needle? If so, when I got the "project", the clip was set at the second slot down from the top. It was running a bit worse there, then I moved it up to the top clip slot and ran better it seems. I also made sure the throttle plunger is able to move up and down with the idle screw and it does.

Is it the nature of these things that after sitting at a stop sign, light, etc that you should be able to just do like a stick car and release the clutch out and give it some throttle and should be able to go, or is this something I should be pedalling to get going again and THEN pop the clutch etc like when I first get it going?

 

[2door]

You need to pedal assist on starts. It isn't a motorcycle and isn't designed to clutch start from a dead stop. Pedal up to at least 8 to 10 mph before engaging the clutch.

The reverse is true when coming to a stop. Disengage the clutch below 8 to 10mph which will allow the engine to idle.

Tom

 

[fabgear]

That explains a lot, thanks Tom. I may or may not give it another run tonight...not sure I feel up to it, but once I do I'll start putting that into practice.