CB350 Hole in Piston?

[stillatwork]

What's up my primarily Japanese bike enthusiast friends,

Got two quick Questions for y'all.

1. See attached picture. Can someone confirm that's a hole in the piston?
2. When I kick this bike over it feels like there's no compression. See question 1. However, rotating the bottom with a wrench, the engine is indeed free, all valves are moving, and things seem OK. Plugs in obviously. Can I pin that on some sort of a kicker leaver issue? Kinda just need to hear someone else say a someone obvious answer before I jump to an obvious bad conclusion. Thanks a lot, cheers.

 

[wahvtec]

I believe it is almost certainly. But if i were you to confirm i would poke a screw driver/skinny tool down and feel for it

 

[Tune-A-Fish]

As evidenced by the clean area adjacent to the hole... Yes it's a hole and from the shape it was a broken off something that landed on the pizton

 

[teazer]

From the small picture it looks like detonation but could just be where a valve dropped its head and smashed its way through. If it's the latter, there is more damage to find and in either case the motor has to be completely stripped and debris cleaned out.

 

[trek97]

Coincidence? Levi just posted this on FB.

 

[stillatwork]

Hahaha! Only thing that could make me laugh at 6:00 before a cup of coffee. Thanks all.

 

[Caf3racer]

From the small picture it looks like detonation

Agreed. It looks eaten away and the color doesn't look like clean aluminum as though a valve had just passed through.

 

[Tune-A-Fish]

Ping ding

 

[wahvtec]

nothing a little quick steel cant fix

https://www.youtube.com/watch?v=uvVvVMnitAM

 

[Kamn]

hahahahah^^

that will hold

 

[teazer]

Plate it. Steel plate above and a few self tapping screws to locate it and she'll be right mate. There was a Suzuki GT750 on ebay a year ago like that and it looked like it had been running with that "repair" for a long time.

Pull the top end off and that will reveal all. Fortunately they are simple motors to work on.

 

[focusinprogress]

if you end up needing, I have two good condition 350 pistons you can have for $25 shipped.

but that looks like a hole to me buddy.

 

[stillatwork]

I bet you I get a lot of shit for this comment, but the engines aren't even worth it getting into. They're a dime a dozen, probably would run filled with sand. Good ole honda. Will probably just part this guy out and throw one in with good compression tune it up and call it a day. Steel Stick review had me cracking up.

 

[datadavid]

Ichiban should cover this subject!

 

[Kamn]

I bet you I get a lot of shit for this comment, but the engines aren't even worth it getting into. They're a dime a dozen, probably would run filled with sand. Good ole honda. Will probably just part this guy out and throw one in with good compression tune it up and call it a day. Steel Stick review had me cracking up.

Best decision you could make, its faster and cheaper.

 

[Tune-A-Fish]

I think if its just detno we need to experiment here.

Roll up a ball of JB Weld just .5mm smaller than the plug hole stick it to the eraser on a pencil and just dab it onto the hole, then bring the piston up to TDC and let it harden a bit, then just run the piston down far enough to reach the JB with a dremel and grind off just enough to clearance the squish... then (this is very important) mix up a hot batch of epoxy steel and drizzle a little on the repair then use a little brush to smooth out... do it real fast or it will harden up onya!

This will need to set for 14.375 hours but then need to run up to operating temps to fully cure... should work, but <-----<<< read my Avatar

 

[teazer]

I bet you I get a lot of shit for this comment, but the engines aren't even worth it getting into. They're a dime a dozen, probably would run filled with sand. Good ole honda. Will probably just part this guy out and throw one in with good compression tune it up and call it a day. Steel Stick review had me cracking up.

I follow the logic, but unless you really know how good or bad the replacement motor is, you are just trading one bad lump for another questionable one. Pop the head off and if you decide it's not worth bothering with, part the motor out - it still needs to be stripped and cleaned to do that.

Off with its head.

 

[farmerdl]

I agree with teaser. Especially if this is a bike you might keep for awhile. With a rebuilt motor you know what you've got.

 

[Tune-A-Fish]

Yeeeep!

 

[Hurco550]

Coincidence? Levi just posted this on FB.

Haha I hadn't even seen this thread at the time