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]

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]

.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 :lol:
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/jj213/DesertDog_12/pavilionandoilfilter045.jpg

http://i273.photobucket.com/albums/jj213/DesertDog_12/pavilionandoilfilter044.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]

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

[DesertDog]

well b-4 i knew anything in this business it was assembled and delivered , the customer called me up the next day complaining, and the complaints never stopped , so i apologized,

picked it up to work on it and see what it was doing , it never dawned on me back then to do a compression test, i messed with the carb for 2 wks , :evil: confused, changed the oil , tore the side covers off, looked at what i could at the time of no experience,
some one mention to me on TT to do a valve clearence check, did that no clearence, you could'nt have put any tool between the valve and lifter,
still no thought of a compression test yet.


after two weeks when delevered to the customer and he gave me plenty of time to fix it and i refunded the guys money back,
my distributor has refused any help .
now that your up to speed.


so it is a high possibility the valves got bent , to me anyrate, cause when i adj. them it finally started easier and you could go with out it dieing when you let out the clutch.

i'll do the wet test as well, leave no stone unturned

thanx guy's for the input

[katoranger]

I would suspect a damaged valve. You may be able to replace just the valve, but it is also possible the cam is damaged.

Best possible solution is a replacement head/valves/cam.

Is this a pushrod engine?

Allen

[DesertDog]

no all is moved by the cam, ie: chain down to crank from cam, i've go some old pics see if i can link it here. the lifters are bolted down to the valve cover, no push rod to actuate the lifters
DD


http://i273.photobucket.com/albums/jj213/DesertDog_12/IMAG1363.jpg

http://i273.photobucket.com/albums/jj213/DesertDog_12/IMAG1371.jpg

[katoranger]

Okay, OHC engine then. The cam may have flattened lobes and you would need the spec sheet and a dial indictor to tell probably.

Possible the the valve stem is bent too.

After the wet compression test let us know the results. That will get the problem narrowed down further.

I am suspecting a bent valve/flat cam from the valves too tight. Most likely an exhaust valve.

Allen

[DesertDog]

okay,
do that when i get off of work , thank you
DD

[DesertDog]

okay,
do that when i get off of work , thank you
DD

did the wet test b-4 leaving for work , squirted about 3 pumps of oil in the cylinder, put the tester on , cranked it over, it went up to 115lbs, did that twice, same both times 115lbs stedy,
so leave a post for me on what to do next and i will check it out tonight, i am late for a date ( my j.o.b.) gotta go
DD

[katoranger]

That indicates rings. It may be that a hone job and some new rings might fix it. It may just need a light hone and then a proper breakin.

If it was broke in with synthetic oil the rings probably didn't seat or it wasn't heated up enough then let cool etc.

It could be that the wrong rings were used etc.

Either way you will need to pull the top end.

This will give you a chance to inspect the valves, cam and head.

Allen

[DesertDog]

hey thanx Kato
some friends at work say the same thing , one told me i may have put to much oil in there and caused the oil to set up on the valves creating a seal , thus giving it better compression, since it did not smoke,

but none-the-less i need to break it down as mention and then i can tell
thanx a bunch.

hey kato can you leave me a post for where to get valves and rings, if and when needed,

DD

[katoranger]

I don't know about parts for a loncin.

Might be a Bruce question.

You would need to call him.

Allen

[DesertDog]

well i found out that this engine (300cc Loncin ) is a look-a-like to the DRZ250 (05), dont know yet on the internal parts per say, Saturday is the break down day, to see what the ? went on inside this motor
could pics be wanted for everyone ? nah!
DD

[katoranger]

I would like pics. If it really is an DRZ copy or relation I may be able to use one.

Allen

[DesertDog]

anyone got a good camera 8O ,
a steady hand ,
this is'nt gonna be like my old 327 chev i take it, that was one of the most simplist motors to work on.

hope this one does'nt give me fits.....

going to brkfst , see ya

[VinceDrake]

Hey there!

Just thought I'd jump in here with some useless info-- If the valves were that tight, 0 clearance, more than likely, the problem is not bent valve, but *Burnt* valve, most likely exhaust. Bent valve would more likely result in 0 compreshkin, normally they hang badly. Burnt valve can kind of seal at low speeds/pressures, especially with a little 10w30 in there filling in the gaps.

If you're interested A couple ways of checking without tearing it apart--

If you have a smoke-machine (Usually only works best on *very* burnt valves)
--Turn cyl to TDC.
--Pull plug and Insert Smoker outlet into the spark plug hole.
--Crank the smoker flow rate up as high as it goes.
--Pull oil dip stick and air filter (Put this step up 3 spots, k?)
--Watch for where the smoke comes out.
--Dip stick hole=Rings/piston/bore
--Carby=Intake valves
--Exhaust=Exhaust Valves

If you don't have a smoker, you can use a cylendar leak down tester, of just hook up shop air to your compression tester, with it in the sparkplug hole, only thing is the crank has to locked in place. This level of air pressure, will tend to move the piston/crank, etc. in gear with the park brake on should work.

--Same set up as previous, But now instead of look for smoke, listen for air escaping, in cases of small leakage,, I've used soap bubles over the carby and exhaust (How to make a China-ride blow bubbles!)

Final Possibility-- The Good Ole Boy Way
I'm Sure I'm going to catch he11 for this but!

--Remove Sparkling Plug.
--Remove Exhaust and Intake Manifold.
--Roll the pistom Before top dead centre about 1 to 1.5 inches
--Fill Combustion chamber with diesel fuel
--Re-install sparkling plug
--Turn Crank by hand towards TDC. *NOT* hard-- Don't want to bend the conn rod! I'm thinking Maybe 15-20 Ft. Lb Torque, max.
--Hold under pressure until diesel drips out somewhere.
-- A crank case full pf diesel indicates rings, and is very messy.

Checking Timing Chain The Good Ole Boy Way!

As Long as we know where there's a 0 mark on the flywheel, that's really all you need.

--So! At TDC We know Both valves are closed, right!
--At 180 degrees of cam rotation (one full crankshaft revolution) The engine Goes from exhaust stroke to intake stroke, correct? Therefore! If you can find TDC, and go one complete crank rotation, as the 0 mark on the crank just passes, the valves should go from exhaust to intake (Flip over, whatever) The point at which both valves are slightly open, should line up with 0 on the crankshaft (Can be measured with screw driver in plug-hole too.) IF it's not, the timing chain is out of time.

So yeah, that was really, really long. Sorry about that. Hopefully you can use some of it, maybe it'll hlp isolate things without having to tear the thing apart. Best of luck man!

--Vince

[DesertDog]

either way i have to take the head off, and i just busted the clutch cover, looks like a round thingy with flat fingers and the clutch plates go on the inside, i have to take this off to remove the nut that holds the timeing gear on the bottom, to get to the chain and remove the chain,,
:cry:

but i do appreciate all that info and i fallowed it very well, thanx V/D

[VinceDrake]

Yeah, either way you're going inside, shortly after I posted, I kinda realized that would have been useful about a week ago-- Kinda Useless now... Sorry About that.

I'll try to be more useful in the future :D

Just for my curiosity, would you be willing to take a couple of shots of the engine when you're in there? I know like, zilch, about the 300cc engines-- Is it about the same thing as the 200cc OHC?

Best of luck with the thing, hopefully it starts treating you decent, man!

--Vince

[DesertDog]

taking shots as i go , found out i did'nt have to remove the clutch at all, two bolts holding the cam gear on took em off the gear came off the cam , took the chain off,
>
>
i will need a know-it-all to help with the puting timing back in place.
i'll follow your tip on that.
>
>
the piston looked burnt (scorched) down the side near the top, inbetween the first ring and the second, is that normal ?,
>
>
piston wall (sleeve) looked very scratched, smooth, but all kinds of swirl scratches, going this way and that, in a downword spiral, is that ok ? yes this the first 4 stroke single cylinder i've tore into,
>
so i guess i will need to order rings, and a clutch cover,

will post pics when all done and i can get parts,
thanks Vince and kato

[VinceDrake]

If it's very low hours on it, yeah, you're going to see some uglies between the top compreshkin rings. (At least that's what I commonly see on auto engines) Mainly as they are still sucking some oil up there, and then in burns and oxidizes and stuff. I think....

One test that might be a good idea though, set the head upside down, with both valves closed, and fill up the combustion chamber with gasoline, or brake cleaner.

The valves should be gas-tight for at least a good 10 minutes. Just to make sure it hasn't got a very small leak in an exhaust valve.

(Just for safeties' sake.:D)

--Vince

[DesertDog]

found this under dealer discution, on the thread of sunnysports
sounded simular to what i found today
comments by montanaoffroader
--------------------------------------------------------------------------------

Actually, when we pulled the head and cylinder off, we found that the rings were stuck in the piston and the piston looked like it had been dragged down a gravel road! The valves were fine.
_________________
87 Polaris Trail Boss 4x4 - Work in progress
__________________

[DesertDog]

ok parts dealers, where are you ?
before i hit the never ending web on dealers that say they have parts,
>
> i want to give chinarider dealers the first come on my order, i know i'm a dealer but i dont have a direct link to my supplier anymore, he burnt me and , now its over.
>
>
i need to get piston, piston rings, valves, and a clutch thingy ,where the clutch plates go on the inside and bolts to.

for a 300cc Loncin engine, its tore down and i need to get the parts ordered, so tell me what you want to know first,

pm me if you want or ask here so all can watch and learn from my mistakes.

DD

[DesertDog]

ok :wink:
i know when i'm not wanted :?
to THE Internet i go
BRBRBRBRBRB

[VinceDrake]

I wonder what the heck happened to it to make the piston/rings look that bad? Hmm.

Maybe someone in the QC department had to poop or something and that one got through....

Sadly, I only do car stuff-- No bikes/ATVs-- Although, I have a really Nice set of Yamahoe RD350 2nd over pistons I could sell ya' if'n ya' want! :D

--Vince

[DesertDog]

yeh vince ifin they'll fit , wut'll i do measure with a caliper, the piston thats on there is probly good, but i will change the rings and valves, thought about changing the head if i could, for a bigger piston ,?
it'ld be sweet if that yammy 350 would fit.
DD

[winnipegmike]

So...how does this story end? Is it working now?

[DesertDog]

yes as the story goes 8) , so do the days of our lives 8O

i will no more on july 14th if the parts came in from china to www.loncin.ca , i ordered thru them and it has been a trying time,

so nothing yet will post any (news) on parts delivered, and attempted assembly being planed .

[DesertDog]

it has been a pleasure to have talked and done some typing and emailing
but life has ended for me

good by

[winnipegmike]

it has been a pleasure to have talked and done some typing and emailing
but life has ended for me

good by

What does this mean???