OX66 Rebuild question for Rodbolt

[Guitar1]

Rodbolt,

I bought a used OX66 225 with 350 hours....Did not run too well so I had my local Yamaha dealer take a look. The compression check revealed "0" on one cylinder. The piston was melted, etc., etc., etc.

The engine was rebuilt ($$$) with two new pistons and 6 sets of rings, etc. It seems to run OK except on occassion it is very hard to start when warm. In addition, it does not run at the "high idle" when started cold. Compression is 95-100 on all cylinders and WOT is 5200 RPM. The motor runs very good and idles very good otherwise with normal oil and fuel consumption.

The LP fuel pumps were not changed at the rebuild and may be the original. All filters, vst, O2 sensor, plugs, caps, were changed at rebuild. Injectors were checked and OK.

Why is it sometimes hard to start when warm and why does it not "High idle" on the first start?

Any help would be most appreciated.....

Sincere thanks,

Guitar1

1998 Yamaha 225 OX66

 

[rodbolt]

Re: OX66 Rebuild question for Rodbolt

wasnt rebuilt, was patched.
by your description.
try to post more info and when I am more sober ill try to walk you through why I say it was patched.
and again, we need a full model number.

 

[Guitar1]

Re: OX66 Rebuild question for Rodbolt

Rodbolt,

Thank you very much for you speedy reply!

Not sure if I would call it "patched." Here's the detail you requested......
Yamaha 1998 S225TXRW Ser.#101862
At the rebuild the following items were done:

1 new cyl. head
1 pwr. head gasket
4 std. ring sets
6 wrist pin clips
1 std.piston
2 50mm pistons
2 50mm ring sets
1 vst gasket
1 vst filter
1 hose clamp
1 oil filter
1fuel filter
1 w/p impeller
1 o2 gasket kit
6 spark plugs
2 wrist pins
1 oil sight tube
2 cyl. bored 50 over
4 cyl. honed
vst cleaned and injector check

Very comfortable with shop and technicians....Your thoughts on hard start when warm (on occassion) and no "high idle" on cold start.

Thank you very much,

Guitar1

 

[rodbolt]

Re: OX66 Rebuild question for Rodbolt

may not always idle high, depends on if the cts sees above or below 113*.
quick check with the diagnostic test lamp will tell you.
was patched.
you simply cannot hone the cylinders and keep it in its .003" service limits.
have you checked the plug caps?
why did it blow up in the first place? was that issue resolved when it was patched?
a rebuild is when you replace or recondition ALL reciprocating parts and at a minimum the bottom crank bearing.
was the O2 sensor output voltage tested correctly?
its a simple system that can drive some folks nuts.

 

[Guitar1]

Re: OX66 Rebuild question for Rodbolt

Rodbolt,

I'm not 100% sure the culprit was found that caused the problem.....The tech's opinion was an injector was clogged and ran the cylinder lean.

I am trying to not "break the bank" with this effort, just want a good running dependable old 2 stroke.

If you can offer any suggestions on what I might do for insurance I would appreciate it.

Thanks again,

Guitar1

 

[rodbolt]

Re: OX66 Rebuild question for Rodbolt

what did the old pistons look like, they will tell the story.
its called piston failure analyisis.
most tech cant pronounce it,spell it or even know about it.
yet they are the first to blame oil injection,injectors or a voodoo doll.
heck I cant even speel it.

looks like to many and not enough parts got replaced.
were the injectors actually sent out for flow testing?
no outboard shop I ever saw actually has that equipment due to the cost of it.
was the O2 sensor output voltage tested PROPERLY?
if the O2 sensor is unplugged OR contaminated the ECU WILL react regaurless.
where does the rod,wristpin and crank bearings get the lubrication on an OX66 motor