buying B400 - checking electrics and compression?

[El Dopa]

Hi all,

I've just been offered a B400v at a very reasonable price after a sale fell through.

The seller has told me that the original buyer walked away after the bike failed a compression test, but he hasn't got (or won't tell) any more details.

I've been through this forum, and it seems like the two biggies that you should be wary of when buying are electrics and compression.

So compresssionwise, what am I looking for? And if it's bust, how much of a job/cost is it to fix?

Alos, the bike has been sitting around for six months or so without  a good ride. Is this goiung to affect the results of the test?

Cheers,

Rich

[stormi]

The seller has told me that the original buyer walked away after the bike failed a compression test, but he hasn't got (or won't tell) any more details.

snip

So compresssionwise, what am I looking for? And if it's bust, how much of a job/cost is it to fix?

Hi Rich,

According to the manual for my 919, if a bike fails a compression test, this can because of:
A valve stuck open
Worn cylinder/ piston ring
Damaged Cylinder head gasket
Seized valve
or improper valve timing.

Honestly?  A lot of this can be taken care of with just labour and your trusty service manual beside you.  (You have downloaded that from the members section by now, right?)

Valves often stick open because of carbon deposits, either on the mating surface of the valve, or on the rod portion.  These can be cleaned up with a little patience and reused ( as long as they are still within spec of course.)

A piston ring may be "fixable" by getting a larger ring, or some of the guys here will tell you since you're in there, have it bored out, and larger pistons put in.  As a female, I'll refrain from that.  

A cylinder head gasket will be as easy as pie to put right.  All you'd have to do is replace the gasket and reassemble.  While you're in there, look at your rings, valves, valve springs, valve seals etc...

Now, I'm not going to address the seized valve, cos it's out of my territory.  I'm not sure at this point what, other than carbon, could cause that. (Especially when you look at how the valve is built and works.)

As for timing?  That's pretty much free.  Pop the cover and check it.  suzuki makes this very easy to do.  Unless of course it's out because of the timing chain (camchain) being out of spec.  That becomes a bigger job.  For that, the cases need to be split.

The biggest part of the job is going to be removing the engine from the frame, if you have to go low enough that you can't do the work with it in the bike.  It took me an afternoon to remove all of the stuff required to pull the engine, and then about another 1hr with the help of two guys for us to get the engine out ( I think it should have been easier than that, but what a bear she was, possibly due to lack of any maintenance before I got her.)

In fact, you can possibly even save yourself some money, if you don't want to do the work, by taking the engine out ( after the diagnosis) and taking that in for repair, instead of the whole bike.

Does the bike run right now?  The reason I ask, is I wonder if the original buyer just got cold feet, and gave an excuse to get him out of the situation.

Oh yeah, and your compression ratio is supposed to be 11.8:1

[El Dopa]

Much obliged.  That's really good info.

Soooo, if I picked up one of those big bore kits, which I see includes pistons, rings, pins, clips, & base & head gaskets, not only would I be sidestepping my (possible) compression problem, but giving myself a few extra horses to boot?

Does that sound reasonable?

[Red01]

Sounds reasonable to me.  

[stormi]

As long as it includes valves and stuff, or as long as your valves aren't the problem.  

Of course, like I said, valves can be cleaned up and reused if they're within tolerance.

Compression can be tested with a compression tester, they can be had for around $20 and up.  Then if you want to get really fancy, there's a cylinder leakage tester, that can help pinpoint the exact reason for the trouble. Those go for $90 and up.  (Based on the prices at a local discount DIY store here in Edmonton)

The biggest problem I've run into is that the compression testers you can buy in these stores often don't have an adapter small enough to fit in the sparkplug hole of a motorcycle.  Most come with 14mm and 18mm adapters.  We need 10 or 12 mm ( I don't know which, cos I haven't measured the plug, I just know that thw 14mm doesn't fit.)  Perhaps one of the boys here can help you out with this. (I'd like to know too)