300cc Loncin eng

[DesertDog]

any ideas out there on what the engine compression should be on a 300cc Loncin wet or dry, cant get any speed out of it tops out at about 30 on the
flats and wont climb a hill to save its life.
it is in (the engine) 86-KMD frame , 4spd trny, every thing turns easy , nothing hanging up, ie: brakes, hubs , axels,.
when i got it the valves were pretty tight , adj those to .008 both exh. and int. started alot easier and was able to get it up to 3rd gear, you cant even spin the tires on it.
at a loss on ideas
DD

[nick780]

is this your 300cc predator ,like the one i got? if it is your engine compression for that bike is supossed to be 8:9:1, im going to adjust my valves on mine soon too i think, so i need to find the right clearece.

[katoranger]

.008 sounds like to much.

.005 might be better.

Allen

[nick780]

i was also thinking .008 was alittle much but i dont know what the clearences are suppose to be on a 300cc engine with a compression of 8:9:1

[DesertDog]

Originally Posted by nick780

is this your 300cc predator ,like the one i got? if it is your engine compression for that bike is supossed to be 8:9:1, im going to adjust my valves on mine soon too i think, so i need to find the right clearece.

no this is for my KMD-86 it has the same engine in it as our Preditor,
i meant the engine compression you know when you take the plug out and put the compression tester in place of the plug turn it over afew times
that, what is that?

[DesertDog]

Originally Posted by katoranger

.008 sounds like to much.

.005 might be better.

Allen

I was told you can go as far as you can untill u here the rocker arms start to make the tapit noise,
but i was also looking at the timing gear when i had the head cover off and i think it looks a little to advanced, the cam lobes where well on there way down when the lifters were opening up, thats why i adj. them to .008 that is when it also started alot easier and have throttle response, and would'nt die when taking off,
so now there is just no power

[katoranger]

.008 may be right for engine. The 8.9 to 1 compression ration sounds about right.

You should have 120-150psi of compression on a never engine. If you got less than a 100psi than you have some kind of valve or piston ring problem. Does the engine smoke at all?

If not smoking than it is probably a valve not sealing well or possibly a leaking head gasket.

Allen

[DesertDog]

Thanx Kato
i was leading to the valve idea my self since the day i got it you could'nt put a feeler gage in between the lifter and the valve,
so i will do the compression test ,,, oh yeah no it does'nt smoke.
i may even take it all down and do an inspection.
just for experience,
then send the motor back since it is still under warranty (1 yr)
DD

[katoranger]

A compression test good tell you alot.

It may also be out of time.

Allen

[DesertDog]

okay , how the heck do you check the timing on these things,
uoo a haf a goot nawige on dees
could'nt resist. sorry
>
i as-su-me (assume) i will need some kinda special timing light for this, and ?
DD


question: you know how you tell if someone is wise,
answer: they have stopped thinking 8O

[DesertDog]

lets see if i mess this up :o 8O :?
ok Nick780,,,, this should help, gives us something to go by.

http://i273.photobucket.com/albums/j...lfilter045.jpg

http://i273.photobucket.com/albums/j...lfilter044.jpg

[DesertDog]

Gawwwwly it wooked ,
a success , one photo is rather large tho there nick
DD

[DesertDog]

ok you 4 stroke engine rebuilders,
did the compression test on my KMD-86 with the 300cc Loncin engine ,
here's what i got , 95psi (lbs) thrice (twice), my preditor walked in and did a whoping, (no italians out there i hope) 135lbs compression.

so Kato did you say it could be valves, and no it does'nt smoke
still under warranty with supersportz, sellatvsnow, powersportsNmore,
all the same owner and no tech guy
he wont return any calls any emails, he'z name is eric. he does the web sites for this business.


on word enough i bit the bullet, am eating crow.

tell me what/how /and where to get the valves,
but first to tear it down and what to look for.

i've been dazed and confused for so long i've got to ramble on :?:

DD

[montanaoffroader]

Dump a shot of motor oil thru the spark plug hole and retest. If the compression shoots up, it's most likely a problem with rings. If it stays about the same, it's prob valves or head gasket. Good luck.

[katoranger]

Originally Posted by montanaoffroader

Dump a shot of motor oil thru the spark plug hole and retest. If the compression shoots up, it's most likely a problem with rings. If it stays about the same, it's prob valves or head gasket. Good luck.

Yep. Try that.

95psi is why you are so low on power.

I would lean toward a valve problem since it is not smoking, but don't rule out the rings.

It may be that they never seated properly at breakin.

How did you break it in? What oil did you use?

Allen