motor runs rich.

[barnstorm100]

Hi, just finished first build with one of those 66\80.
When I run it, it runs very fat like it needs a smaller main jet.
is this common to run like this?
Thanks for help\advice

 

[2door]

It is very common. However the conditions you see are also consistent with a new engine. The little Chinese 2 strokes require about 200 miles, or more, to be considered 'broken in'. It takes time for the rings to seat and compression to build.

If you're using the kit instructions about fuel/oil ratio and mixing at 16:1 you'll want to change that and go no more than 24:1. 16:1 is TOO MUCH oil.

Be patient and put some miles on the engine before worrying too much about fine tuning the carburetor or maximum performance. There is a lot to read here on 'break-in' procedures, proper oil/fuel mix and other subjects you might want to read. Use the search feature and you'll get plenty of advice on any subject.

Also, welcome to the forum.

Tom

 

[barnstorm100]

Thanks tom, for the quick response.
That's what I was doing then read in another thread it will carbon up
I'm running echo power fuel 50:1 with additional echo mix oil so it's at 25:1.
Probably run it at 32:1 after break in

 

[maniac57]

Put the needle clip in the second slot from the top (one less than full lean) and wait for it to break in before tuning the jet size.
When you get it broken-in, I usually find they like at least two sizes smaller on the main, depending. But I solder and drill my own so I have NO IDEA what size mine likes. But they ALL want a smaller main in my experience.
Remember, the factories don't care HOW your engine runs, as long as it makes it past warranty, Hence the TOTAL FAIL on the 16:1.

 

[barnstorm100]

Thanks manic
see, I thought I had heare everything. Ive drilled to larger size but that ruins the nozzle shape. Are the main jets hard to get?
Thanks because that's what I was thinking.
I had some time today and when my bike gets to 25mph it's like a Rev limiter kicks in. Does this have a Rev limiter? If it only goes 23mph, I don't care as long as I know it's ri ght.
thanks again, great forum

 

[MotorBicycleRacing]

Thanks manic
see, I thought I had heare everything. Ive drilled to larger size but that ruins the nozzle shape. Are the main jets hard to get?

Drilling the jet hole bigger is making it run worse.
you need a smaller jet if anything.

The stock jet in an NT, Speed carb and the Runtong is a 70 jet with 5mm threads.

Moving the clip on the needle one notch higher should make it run right
without changing the jet to a 68.

Sick Bike Parts sells the 5mm threaded jets.

 

[maniac57]

I agree. Drilling the jet makes it even richer which is the reason yours won't pull right.
Stick a stock undrilled jet back in it with the clip where I told you and wait until it's fully broken in before you try tuning. Use the time it takes to read up on carb tuning so you will know what you are doing next time!

 

[crassius]

I've seen new engines go less the 20mph for the first 25 or 30 miles (and use a whole tank of gas to do it) - usually after 60 miles you're close to what it will be like when finished running in.

 

[barnstorm100]

I agree. Drilling the jet makes it even richer which is the reason yours won't pull right.
Stick a stock undrilled jet back in it with the clip where I told you and wait until it's fully broken in before you try tuning. Use the time it takes to read up on carb tuning so you will know what you are doing next time!

sorry I wasn't clear. I didn't drill the jet on this but on other motorcycle engines that ran too lean and didn't have money to buy the right jet. I did move the needle clip second to top when I first got it and helped.
what really surprised me was running out of gas the first day I rode. I mean it was rich

 

[crassius]

a lot of that probably wasn't so much rich as just blowing past the rings

 

[barnstorm100]

I couldn't wait and with only 40 miles on it, I put one of those flat slide carbs on. It came with 5 jets so I'll start leaning it out aft r another 30 miles. Also got a banana pipe that I'll put on in a while.

Thanks for the help on the rich running stuff

 

[crassius]

put on pipe before tuning carb

 

[2door]

Barnstormer, regarding the needle clip position, keep in mind that the needle only controls fuel flow at or below 3/4 throttle. Anything above that is determined by main jet orifice size. At WOT the needle is raised essentially out of the orifice so the clip doesn't really have much, if any effect on wide open throttle performance.

Again I'll stress not getting too impatient and making changes until you have some miles on that engine. 70 miles, in my opinion, isn't considered fully 'broken in. I like to see at least 200 miles before starting to tune for performance. But that's just my opinion, and not carved in stone.

Additionally, if/when you make changes, make one at a time. That way you'll see what that change does, good or bad, and you'll know where to go to correct it if it's wrong. Changing carburetors, adding expansion chambers etc. is all relevant to how the engine will run. Doing too much at one time can confuse the issue if performance suffers.

Good luck and keep us informed.

Tom

 

[barnstorm100]

Barnstormer, regarding the needle clip position, keep in mind that the needle only controls fuel flow at or below 3/4 throttle. Anything above that is determined by main jet orifice size. At WOT the needle is raised essentially out of the orifice so the clip doesn't really have much, if any effect on wide open throttle performance.

Again I'll stress not getting too impatient and making changes until you have some miles on that engine. 70 miles, in my opinion, isn't considered fully 'broken in. I like to see at least 200 miles before starting to tune for performance. But that's just my opinion, and not carved in stone.

Additionally, if/when you make changes, make one at a time. That way you'll see what that change does, good or bad, and you'll know where to go to correct it if it's wrong. Changing carburetors, adding expansion chambers etc. is all relevant to how the engine will run. Doing too much at one time can confuse the issue if performance suffers.

Good luck and keep us informed.

Tom

Thank tom, know about carburetors after 42 years. I'll wait till 200 miles to tune.
it is running better than it when it was new.
got a tach and did about 5200rpm. Not sure what r pm to expect after broken in

 

[barnstorm100]

I went down to 60 size main jet and I think the motor with finish breaking in. I've taken it up to 5800 a couple times for a short time

 

[crassius]

be aware that they often go much leaner once they run in a bit - keep an eye on it

 

[barnstorm100]

be aware that they often go much leaner once they run in a bit - keep an eye on it

Thanks, will do

 

[Inf3ct3d89]

engine is bogging out at the 64 jet size I didn't the whole balls deep throttle and remove the plug dance. The plug is coming out of the cylinder a little wet and there's some fire around the plug hole so I'm wondering if I have to go lower than that to a 61 or 62 as well

 

[Inf3ct3d89]

Fuel*

 

[crassius]

if you're leaking around the plug, then usually it isn't tight or the compression ring on the plug is bad - worst case bad or cracked head near plug

 

[Inf3ct3d89]

I bought a brand new head, came in today. Right now I have a 64 in her. Maybe this photo might help diagnose my problem. There wasn't any around the plug this time. I just ran WOT I'm getting about 22 23 mph and it acts thirsty. I have the RT carb. I read that it gives everyone **** at first.