Ec 300

[hannesd]

piston slap... top end rebuild...

hi guys,

i live in belgium and i own a 2000 EC 300 since recently.
bought it for a reasonably low price.
i like the torque it has when climbing small trails

i just hear a knocking ,but only when engine running at idle.
sounds like it comes from the right-hand side.
just opened up the right hand side cover.
found a nearly new clutch basket and plates too.
inspected the PV mechanism and that seems ok (but not like new).
been thinking it could be the top end bearing that's gone,but wouldn't i hear that all the time then,?
main bearings seem ok when pulling up and down at the flywheel,allthough i found quite some axial play (maybe like 1-1.5mm?) dunno how much is allowed.

compression is pretty low too, i guess,al least for a 300, i can kick it with my lightest sport shoes

rebuilding itself is not really a problem for myself.
it's rather getting the right pieces ,since there are not many dealers and the one i contacted didn't contact me back.
they don't seem interrested in gasgas anymore...

anyway, any thoughts on the knocking at idle?
can i re-use the gaskets (in case i can't find new geskats quick enough)?

ciao, hannes.

 

[widebear]

Piston slap.

 

[hannesd]

Piston slap.

piston slap as in : too much clearance between piston and cilinder?
i'll take the top end apart asap.
hope to find the problem there, install a new piston and rings and off i go, or in the worst case,get the cilider treated with new nicasil layer...

 

[widebear]

It's been my experiance that on a big bore, that if your rings are sacked there is a very good possibility that the piston is also out of spec. Check for carbon creep past the rings and shiny spots and verticle scars on the thrust side of the pistons skirt.

 

[hannesd]

allright, so i took the top end apart
this is what i found...
alot of play on the piston bearing (small-end?)
the litlle axle thrue the piston was pretty worn out.
alot of blow-by under the piston rings and allso alot of piston slap as widebar stated
al shiny spot on the top of the piston is to be seen an very litlle scrapes in the cilinder wall though
i did a rough measurment of the piston and i got 71.5mm allover but the cilinder measured on the to and bottom i got 72.2mm
that means 0.7mm piston slap
piston ring gap was 0.85mm...
if you look at the pic of the cilinderwall i made (not very sharp) but notice a matt grey spot around and next to the exhaust port,would that be the layer of nicasil worn off? or can i just orde a "C" piston and slap everything back together?
i did allso find the thick 0.35mm base gasket, i'm planning to use only permatex (or what's the correct name for the stuff?)

let's hear what you guys have to say

 

[widebear]

It may be possible that the nikasil is worn off and the cylinder is ovaled , out of spec, I would recomend you have it profesionaly measured. The problem with deleting the base gasket and using an anorobic sealer on a worn cylinder is, if you have a ridge at the top of the cylinder and its in spec above the ridge because its never seen wear, and your going to fit rings to a larger ovaled bore below the ridge. The ring end gap will be inconsistent to the total bore and you could snag a ring.

 

[hannesd]

could i get a bigger piston to fit the larger bore?
i don't think i can make a "C" piston fit snug enough.
maybe a complete cilinderkit available on the net?

 

[widebear]

Thats an option for sure. Either 300 cylinder and piston or 250 cylinder, piston and head.

 

[hannesd]

Thats an option for sure. Either 300 cylinder and piston or 250 cylinder, piston and head.

250 is not an option since i don't like a snappy bike.alltough the 300 can allso be
any idea on the price of a 300 cilinderkit? and where to get it, don't want an OE one... $$$ :-s

any idea on crossover pistons that fit the same small end too?

 

[iancp5]

Maybe you can get it replated into spec?

 

[hannesd]

got the cilinder shipped to be replated.
hope i'll have it back soon.
allso going to try to make a flywheelweight to add to it, to make it smoother too.
it's one with the very small ignition flywheel, might have been an ex-XC prehaps?
mine's kinda snappy, too much for my likings...
put some new oil in the forks too and getting another shock since the old one won't come apart to rebuild :-s

hope to ride it good from then on...only had it for 3 weeks and took it for 4 rides only when i found out it needed a new top end rebuild...

anyway cheers guys, hannes.

 

[hannesd]

so i got the cilinder replated and installed a new piston.
good copression now and much less fuel consumption too.

the "knocking" noise, that made me start this thread is still there.
but i may have found the problem.
the "knocking" apprears at idle and goes away when pulling the clutch lever.
took the clutch basket of today and found the aluminum part of the basket (with the fingers) moving somewhat separate from the iron gear ring attached to it. (see pic)

i found on the forum here,that someone else took the rivets out and used some M5 bolts to fasten the whole thing back together instead of some lousy rivets...
i'm gonna go that way and inspect the cush drive too inside the hub since i feel something might be wrong there too .

allso found alot of play (+-1/4th of a turn) on the clutch-axle ,when clutch basket is off.
so that means the tranny has that much play... but since it's in 1st gear ,it could be normal to let the tranny shift easier from neutral to 1st.
didn't check if that was the case in 2nd gear allso. will check that asap.

all input appreciated,
thanks, hannes.

 

[hannesd]

found out that the rubber bushings inside the clutch basket were worn out, new ones on the way. hope that solves the noise i heard.

 

[case-racing]

clutch

can you take some pictures and explain what you do when you put the bolts in instead of rivets please.

Cheers Bill

 

[hannesd]

can you take some pictures and explain what you do when you put the bolts in instead of rivets please.

Cheers Bill

i knew i'd have to take pics, but i forgot

drilled the holes ,where the rivets used to be, with 5mm drill.
i took some M5 bolts with a conic head (inside of the clutch basket allready has conic seats where the rivets used to be) and put the nuts on the side of the pics listed above here (= facing inside the engine when clutch basket installed) and had the nuts spot welded to be sure and then flattened for clearance of the cases. (no more then 4mm height!)

hope this is of any use to you.
the knocking noise i had, is gone now

good luck.
hannes.

 

[hannesd]

so my story continues...
i opened up my top-end to measure cilinder (just been replated -10hrs) and new piston.
piston is a vertex "A" piston 71.93mm, cilinder measured i get about 71.99mm (as STD) still i feel alot of free play between piston and cilinder (see vid)

View My Video


i allso did a compression test with a guage i don't know how accurate it really is. i got 210psi ! this is quite alot.
then went to measure squish wich came down to 1.6mm, i guess previous owner must have done something with it allready,as far as i can see compression chamber has not been changed.


the reason why i started measuring everything was because i had the impression that the engine ran at idle like it had low compression.
i must say, it doens't idle very well.
i guess the PJ is too big i assume : 40
MJ is 175 and needle is ne1f and needle is set at it's lowest (highest clip).
i do mostly single track so low revs and it's 4-stroking a.i. running too rich until i open throttle some more, from past 1/4th open it's running smoother.
i was thinking about going to PJ of 38 see how that made it run down low the revs.

let's hear what you all have to say about this...

thanks, hannes.

 

[hannesd]

seems like i'm running this thread on my own
responding to my own posts

anyway,the clearance piston to cilinder seemed to be perfect afterall so i put it back together...
now i'll try to sort out the jetting, blubbery down low...
play with PJ and needle position.

what i was wondering is,if the 200-210 psi wasn't a litlle high when i did compression test?

thanks again for any input...