|
|
TTR125 smoking
|
I am having trouble with a TTR125L 2001 model. It came in smoking.
Upon dissassembly, I found lots of wear in the cylinder. I replaced the
cylinder, rings etc... with new Yamaha parts. I followed the prescribed
break in procedure in the service manual. It still smokes after it gets
|
Have you ever heard of the Bon Ami trick? Old time mechanics used to
dribble kitchen cleanser into the carburetor throats as the engine ran
at high speed. The abrasive particles would help seat the piston rings.
As I recall, Chrysler had a terrible time with ring seating on their
Plymouth models in the 1950's. (1) But old time mechanics straightened
out the problems with Bon Ami.
|
I really think that cylinder, piston and ring technology has moved on in
the intervening half century, mark you.
|
Trying this technique is totally up to you, and DO NOT try it on an
engine with a cylinder that has a chrome plated or Nikasil bore, you'll
ruin the cylinder. Only do this to engines with cast iron or steel
cylinder liners.
(Daddy, what's a Plymouth? I dunno son, ask your grandpa about
Studebakers and Packards and Edsels and Ramblers.)
|
|
OK hold on here,
You said:
"..Upon dissassembly, I found lots of wear in the cylinder. I replaced the
cylinder, rings etc... with new..."
You said you put a new cylinder in, but did you by chance use a micrometer
to
assure yourself that it was, in fact, round? And that it was the right size
for the
piston? And did you mic out the piston? Did you install the rings in the
cylinder
without the piston and measure the ring gap to be sure it was in spec? Did
you
run a cylinder hone to put an initial crosshatch on the cylinder?
Just buying new parts does not relieve you of the responsibility to measure,
if you just assumed the new parts would all fit perfectly, you are asking
for
trouble.
Maybe instead of putting a worn piston with new rings into a new cylinder,
you should have bought a new oversized piston and rings, and bored out the
|
I used all new parts. I did not run a hone to cross hatch as it had a
cross hatch pattern in it already. I did put the rings in the cylinder
and check the ring end gap. I did not measure the cylinder and piston
since the rings were pefect and they fit the new piston. I always
thought that using brand new factory parts was the best route. I
thought that having the cylinder machined was an alternative when
trying to get out cheap.
So do I need to take it back apart and cross hatch the cylinder with a
hone and replace the rings and try again?
|
Did you do a compression check or leak down test?
If it has good compression and passes a leak down test, that will pretty
much tell you the rings and valve seats are OK. You don't want to do
another ring job if you don't have to.
I'm not sure how the oil is run up to the top end of a Yamaha, but on my
Honda thumpers it is run through the casting of the cylinder and
requires O-rings be placed on studs. More then one owner has had
problems with leaving out these O-rings or putting them in wrong.
If it really smokes bad when you first start and cleans up in a minute
or two I would tend to blame it on valve seals.
What I am trying to say is there are other reasons an engine will smoke.
Make sure you check those out too before you proceed.
|
|
Well, actually, since the 1980's. Japanese motorcycles have been built
with a very fine finish in the cast iron or steel cylinder bores and
the piston-to-cylinder wall clearance has been very small, like about
1/1000th of an inch or maybe 0.0015.
Since you don't seem to be the owner of this machine, it's possible
that it has been "repaired" by some old time mechanic who just
*ass*-umed that a cross-hatched hone pattern was the way to go, using
the older theory that the honing left scratches that held needed oil
during breaking.
My friend who owned a motorcycle speed shop bought a special Sunnen
hone that micro-finished the over-bored cylinders that he was supplying
for his customers when all the rage was big bore kits for drag racing.
When he went out of business, another friend bought the hone.
If you decide to buy a whole new cylinder and a new piston and rings
(or overbore the cylinder you have and use the next sized piston and
rings), you still need to
"mike" the parts to find out what the clearances are and compare them
to what the shop manual recommends.
"Miking" the bore of a cylinder requires either a telescoping bore
gauge or a set of external machinist's dividers. After expanding the
bore gauge or dividers to the internal diameter of the cylinder, they
are then measured with a large micrometer, perhaps a 2 inch to 3 inch
micrometer in your case.
If this all sounds complicated, you might want to place yourself at the
mercy of a motorcycle machine shop.
But, first ask the old geezer in the shop if he still believes in
honing cylinders with a cross-hatch pattern... ;-)
|
I really was trying to achieve a like new result.
|
cylinder?
|
hot.
I then pulled the head and swapped it for another from another bike,
thinking that it could be valve seals but it still smokes after it gets
hot. No change.
What should I check next?
Any help would be appreciated.
Lindel
|
|