It may be a rod bearing , or , since it varies in rpms , very well could be
the right side crank bearing . This will cause the seal to leak , creating an
air leak . Is there any moisture around the flywheel side ?


 
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--- On Tue, 6/9/09, Mark <mtdewd@...> wrote:


From: Mark <mtdewd@...>
Subject: [YamahaIT] IT200 Diagnosis Help
To: YamahaIT@yahoogroups.com
Date: Tuesday, June 9, 2009, 1:55 PM








Hi all,

Just found this group. I'm having issues with my IT200. It's a 1985, with the
with the big-bore 240 kit. I just put a new piston in it, and had the bore
freshened to fit. I only rode it for maybe an hour after I bought it before
tearing it apart to rebuild. The piston had a LOT of clearance and some scoring,
so I figured I'll start fresh. So I have no idea if this issue is new or not.

It's making this clacking sound, that sounds just like the sound of tapping a
wrench on the flywheel case cover. It's hard to explain, so I did a short video
where I was intentionally trying to make it happen. http://tinypic.
com/m/2l5q9y/ 4

Someone suggested chain/sprockets, so since those were indeed worn, I got a new
set. That helped a lot, but now the clacking sound seems strictly internal. It
does it at idle in neutral, which is my next question.

After warming it up, and riding for a few minutes, it starts to surge (?) real
bad at idle. I stop, put in neutral, and it sits there and does regular and very
quick rpm spikes. When it spikes, it makes that clacking sound too. I've tried
spraying carb cleaner around head and base, and on every seal and joint I can
see, including behind the flywheel. No changes. If I hit the choke, it stalls. I
raised the float level a bit, and it poured gas all over the driveway, so I
redid it as carefully as I could to set it at spec, which was a lot lower level
than I had it. No change.

Also, if I get it at a crusing speed, say in 3rd gear, and hold the throttle to
just where it's maintaining speed, it will start clacking madly away. It has to
be accelerating or decelerating at all times or it makes that sound. On decel,
with throttle closed, it will start surging, which gets weird, especially going
into a turn...

Sorry I don't have enough experience to give better descriptions. Any ideas at
all? I've pulled off the head and the flywheel cover, and all looks normal. Is
it going to explode on me? I'm starting to be afraid to ride it.

It's the highest octane pump gas I could get, and I even bought octane boost to
try in this last tank. All gas in the state has 10% ethanol, if that matters.

















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