Problem with new build.

M

Muddy

Guest
I bought the 2-cycle engine brand new and put it on a brand new bicycle. It looks good. The fuel is properly mixed. I checked for vacuum leaks by spraying starting fluid around the manifold and such places that might suck air. It's nice and tight, any vacuum leak the engine would speed up and it didn't. That's good.

Here's what I'm dealing with, the problem is that the engine won't speed all the way up. Since it isn't up to speed it also isn't up to power. Everything is brand new, not even through the first full tank of fuel yet (16:1 break in ratio). It will barely pull me on a level surface, any kind of grade is out of the question.

I'm open to any and all suggestions, please help.
 


gary55

Well-Known Member
Joined
Nov 27, 2012
Messages
3,509
I bought the 2-cycle engine brand new and put it on a brand new bicycle. It looks good. The fuel is properly mixed. I checked for vacuum leaks by spraying starting fluid around the manifold and such places that might suck air. It's nice and tight, any vacuum leak the engine would speed up and it didn't. That's good.

Here's what I'm dealing with, the problem is that the engine won't speed all the way up. Since it isn't up to speed it also isn't up to power. Everything is brand new, not even through the first full tank of fuel yet (16:1 break in ratio). It will barely pull me on a level surface, any kind of grade is out of the question.

I'm open to any and all suggestions, please help.
Drop the oil mix to 6 ounces to 1 gallon. I know the instructions say 16:1, but that is too much even for break in. After 1st gallon drop to 4 ounces per gallon. Check torque on head bolts, 12 lbs., check compression. If comp. is good try running it with lighter mix. If still weak jetting may be needed. Often really weak performance on a incline is a compression issue.
 

Lukesky36

Active Member
Joined
Oct 3, 2018
Messages
432
Just run 30:1 i do it with all my new motors and yet too see any issues with it just don't run it hard at the start
 

Greg58

Active Member
Joined
Jun 3, 2012
Messages
258
It's a good idea to check the spark plug gap, or better yet change to a B6HS NGK. .26-.28 runs good for most.
 
M

Muddy

Guest
Thank you to everyone who responded, I truly appreciate it. I'm going to give it another test run after I mix up another batch of fuel. There were two suggestions, one being 6oz of oil to a gallon and the other suggesting a 30:1 mix. I'm going to shoot between those suggestions with 5.5oz to the gallon of fuel and see how that works out. As to the suggestion concerning the plug I have already swapped it out for an NGK B5HS (properly gapped) hoping that would work with no improvement. I did not check the float level because the engine isn't running out of or starving for fuel, or at least isn't showing anything along those lines. That will be the first thing I check if this doesn't change the performance. As a side note I put the electrical system on a multi-meter which showed 355Ω which is only slightly high, but I ordered a replacement anyway.

I'll let everyone know how well this works.
 

Greg58

Active Member
Joined
Jun 3, 2012
Messages
258
If the sound is not a problem do a test run with the muffler cap off, if the jetting is Rich it should run better.
 

Big Muddy

New Member
Joined
Jul 5, 2019
Messages
3
I don't know why I wasn't logged in before, but am now. Ok, it did run a little bit better with less oil and high test non-ethanol gasoline, but it still didn't run as good as I expect.

I had already tested it with the cap off the muffler, which didn't help much so I put it back on. I had made up a better gasket for the carburetor manifold to insure it wasn't obstructing the flow (I had torn the original) and tested for leaks afterwards.

I have not checked the exhaust gasket to see if that's obstructing the air flow through the engine. I have moved the clip up and down on the needle with little impact to performance.

Could it be that the carburetor that came with it is just crap? I'm asking because I don't know.

Here's what's bugging me. I have a long history of working on small engines, and such since the early 1970's. I was "the mechanic" at the local motorcycle shop when I was 17 years old. I've rebuilt automotive engines and many small engines. I'm not used to being stumped by a small engine. I'm not used to being stumped by any engine at all, yet here I am like a 12 year old kid with a handful of tools without a clue as to what I'm doing. This is frustrating!

Bicycle 3.jpg
 
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