Help me with my k@b,cant keep rpms up

[bob miller]

james , have you ckecked your bearings ? i soak my motors in denatured alcohol and turn motor over by hand and feel for any roughness , before you turn motor over by hand add some oil to the piston and sleeve to prevent any damage to the p/s fit...bob

 

[Ted buckley]

James, sounds like your P/L is at the end of it's "Pinch". I had an OS that acted this way, and after checking all the points mentioned in the previous posts, I did a compression test on it, and it was done. Fortunately, the P/L in the OS was still good(ie. No scoring/pitting etc.), so I had a friend of mine - that was a machinist build a squeezer for the liner and tried that. Engine worked good again. Not saying this is definately the problem, but have you done a compression test on it?

 

[James montgomery]

Have not done that yet but i will do that to see if it is that, still feels good as far as.compersion but will try it and mske sure,know any one i csn send to to have repinched

 

[Kez]

. I could blow very little air throw the carb al the way closed. So changed that out and will try a bench test here in a little bit.

I think you misunderstood what I was suggesting. I have had carbs from K&B where the needle does not close completely when the needle is turned fully in. There should be no fuel flow at all when the needle is fully closed. In my case, the brass piece that the needle valve thread into was machined off. So when the needle is turned all the way in, it was not closing up the venturi (spray bar).

If you have one of these carbs, you will be running very rich. Becasue at 3 turns out, you are probably running a lot richer. If you are able to blow into the fuel nipple with the needle valve closed all the way, (this is regardless of the barrel position), you probably have a bad carb and running rich. Try leaning a quarter turn a time and see if the RPM picks up.

 

[Ted buckley]

Have not done that yet but i will do that to see if it is that, still feels good as far as.compersion but will try it and mske sure,know any one i csn send to to have repinched

I had someone else build my P/L squeezer - long ago :lol: :lol: . Here is a link:

http://woodrcboatproducts.com/page7.html

 

[James montgomery]

Ok so now i think i have a bigget problem now, i did everything u guys have told me to cheack and now my p/l is really fit seem so **** tite now should this be happing or is it fried, it was not like that befor

 

[James montgomery]

The fit seem so tite now and was not like that befor

 

[RodneyPierce]

James, have you been running it and just revving it up there with no load on it? Thats a good quick way to ruin a motor...

And what fit are you talking about? Piston to liner fit? It doesnt just get tighter by itself.

 

[James montgomery]

The last few times no load on it,.exsept fir yesterday at the little pond by my house, yes the piston to liner fit seem to be really tite now any ideas y

 

[RodneyPierce]

is it hard to turn?  Take the power head off the lower unit and try and turn it by hand.  You could have very possibly ruined your flex shaft running it like you have been (especially with no lubrication).  Or you may have other internal motor issues.

 

[James montgomery]

Yes it is hard to turn, the fir seem so tite now

 

[James montgomery]

Yes it is hard to turn but only at tdc, other wisr it is nice and free other then tdc even without glow plug in

 

[RodneyPierce]

did you try and pinch it with something? Take the water jacket/head off the motor and look at the top of the sleeve and piston.

 

[James montgomery]

Ok wht am i looking for whn i take it off , no never tried to pinch iy

 

[RodneyPierce]

just look for damage. Did you scuff the piston? There has to be a reason it got tight all of the sudden.

 

[James montgomery]

Ok will look

 

[James montgomery]

Ok so there is some scoreing on the exsaute side of the piston im gessing my moter is screwd now

 

[RodneyPierce]

how deep is it? Take a picture and post it.

 

[James montgomery]

Ok give me awhile my ac is not kivking in at home , will get thos pics up as soon as i can rodney

 

[Hayden Bright]

It could also be nothing to worry about....like rodney said check your flex shaft is ok first, from my experience doing some bench test may yeild a tighter P/l fit because your running the engine a little hotter than normal and when the engine cools down the fit seems tighter.

I have noticed this with my OS if you do a bench run i'll monitor temps so they don't get to hot say, 200 degreesF and later after the engine has cooled there will be a nicer fit, as in it's harder to turn over the engine by hand ...just from my observation's this is quite normal...

My 2 cents.... could be nothing to worry about at all james as a tight p/l fit is a great thing to have.