CB360 smoking badly

[jzanutto]

Hey guys I've rebuilt several bikes but this CB360 is absolutely puzzling me. This thing smokes like an airplane at an air show out of the left side only.

I picked up the bike really cheap, and have completely rebuilt the bike from the ground up. The bores are still at standard, no deep scratches. So it's got a fresh hone and new rings, the bores are round not oblong. Cylinder to piston clearance is at about .005". I re-used the pistons. Ring gaps are properly staggered.

The head has new valve stem seals, and the valve guide to valve clearance is good, no wobbly valves. Nothing about the assembly was out of the ordinary that would seem to cause this.

This is my first CB360 build, so I have to ask is there anything special about this engine that would make it draw oil into the cylinder?

I have the orings in place at the base of the cylinders, I have the orings in place that are between the cylinder and head...

so WTF? I don't really see why this thing is smoking like this..

 

[trek97]

bad valve seal, bad valve and/or seat, broke/overlapped oil ring, scored piston/bad rings, bad head gasket/head seals.

bummer

check compression. if low, add a teaspoon of oil to cylinder through spark plug hole. If it raises= points toward rings, piston and/or bore.

If compression does not rise w added oil = probably at valves, check valve/tappet clearance.

 

[xb33bsa]

it is what it is ,broken or knackerd oil ring is the only ring thing that will make it smoke that badly
and it will not cause low compression
a compression test tels you nothing about the condition of the oil ring neither
when i got got my 350 it smoked like a bastard on the one side,it was a brand new bore and the comp was excellent
whoever put it together broke the oli rang
on another note .005 is to much clearance get new 0/s pistons and bore it fercripes sakes

 

[crazypj]

Valve guide seals make them smoke like a stroker after putting round town all day then opening up on the bypass
Exhaust seal usually fails first (it gets hotter and it's 35+ yrs old)
Oil in the hot pipe is a James Bond trick for smoke screen ;D
Seal could get dislodged or damaged if not fitted properly, I just re read first post, if your 100% sure the oil ring didn't get trapped (very common if you haven't done them before) check engine breather isn't trapped, kinked or ootherwise unable to work (although that normally causes ALL the seals to leak as well)

 

[xb33bsa]

how come a 350 uses no valve seals and dont smoke real bad ? he says it smokes super bad that aint a valve seal unless the stem to guide clearance is fubared pretty bad AND the seal came off,the culprit is the oil control ring

 

[crazypj]

360 has a much better oil pump (too good) at medium rpm it pumps a shitload of oil to top end.
Intake seals will pass oil if you chop throttle and change down creating high vacuum, sometimes blipping throttle is enough (when guides are worn)
The highly scientific method of 'looks OK to me' doesn't mean guides are good
0.005" piston to cylinder clearance is excessive, I run mine at 0.0015"~0.0017", even the 378cc motors.
IIRC, 350 had a tapered top to valve guide so oil tended to run off?
It is more likely he screwed up oil ring though.
Many (many) years agoI was at Honda UK for a course, instructor told us the class from week before was doing CBX 6. one 'professional' used a dead blow mallet to fit cylinders, trashed all the rings and the cylinder - they sent him home as hopeless case (and he failed course) ;D

 

[jzanutto]

The valve guide seals are brand new.

Rings are new as is the hone. I've had it back apart to double check the hone when it smoked after the first assembly, and the rings are just fine, not broken. I've put too many engines together to break a ring. And thats why this one is kicking my arse... everything that would be normal on any other engine build is proving to be now in question.

I'm starting to wonder if something is cracked and opens up when it gets hot. Obviously it's got to come back apart

The pistons, rings, bore, hone are identical left to right. The right isn't smoking, it's just the left.

 

[crazypj]

Pull the valves out and check seals are still in place.
I've seen them fitted with sockets, bit's of tube, etc and the top separates from the bit holding onto guide.
Did you use moly grease inside seals for start up lube??
The oil ring 'rail'doesn't break, it's spring steel with chrome face and gets 'folded' over

 

[jzanutto]

yeah I lubed it up. I guess I was hoping someone would tell me about an oil tube or oring that I left out.

This was supposed to be a re-ring/hone and keep going. But I guess we're going back for some wisecos and fresh bore. The cylinders still measure at 67

 

[jzanutto]

more

 

[jzanutto]

you see why I'm pissed.

I put a lot of attention to detail in this POS

 

[crazypj]

If your going to bore it, do the GS850 piston mod
I think I have some almost new 1.00 OS pistons with only 2~300 miles on them, may have a few stock 67mm with less than 1000 miles as well. Have you measured pistons? 0.005" is really too much. If bore isn't worn the pistons must be. (I only have 69mm-378cc motors)
To be honest, once modified, 360 is pretty reliable engine wise, electrical system is usually cause of 'gremlins' although I haven't had any problems with mine (except lack of use killed battery)

 

[jzanutto]

I came up with that number by measuring.

you wouldnt think that with new rings it would be a big factor.

on the right cylinder it was a hit, on the left a miss.


if I do the GS setup, how do the stock carbs respond? you see what pipe I have on it, the 2 into 1 MAC

 

[jzanutto]

my lower back and neck look just like your avatar

 

[Sonreir]

Stock carbs work OK on my 378. Not great, but passable.Jetted up to 118 secondaries. Upgrade in my future to VM28s at some point.

 

[trek97]

I put a lot of attention to detail in this POS

It looks pretty nice to me, in the pics. Sorry you feel that way.

You might have left out the o-ring tween the head and jugs and/or head gasket failed.

 

[xb33bsa]

It looks pretty nice to me, in the pics. Sorry you feel that way.

You might have left out the o-ring tween the head and jugs and/or head gasket failed.

that oring missing wont cause smoke/burning oil like he has described not at all actually, neither will a bad head gasket

 

[xulf13]

I think XB is right,
I have the same exact issue on my CB450. I put a lot of attention to the right piston because it had a slight scoring and did not even check groove clearances on the left piston. Compression is great on both sides (180psi both sides) so I was puzzled.

I would remove the jug and check for a dark streak running down the length of the cylinder that's smoking. That's were the middle ring and oil rings are not doing their job and making your bike smoke like a train. At least that's what I just found out on mine.

Got new rings and gasket set on the way and will make sure I clean the groves really well and install rings, compress them in the grooves by hand and make sure they spin like they are supposed to. They need to move freely without dragging or having resistance. That will cause the rings to stick on one side after you install them and heat is applied.

 

[jzanutto]

I think I'm just going to bore at this point. If it's coming back apart again might as well go all the way

 

[jzanutto]

BTW how does the oil get up to the top end??? whats the passage?