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CB350 rebuild questions

GaryJames

GaryJames

Veteran Member
Joined
Jul 7, 2022
Total Posts
311
Total likes
110
Location
Auckland, New Zealand
Have progressed quite quickly in getting the transmission and lower crank case assembled.
I have two questions please.:
1. When fitting the small rubber ball in the lower case I found it was a reasonable firm fit. I had though that it acted like a loose valve moving within the confines of its home in the casing with oil flow.
The one that came out during disassembly was not perfectly round and had 2 x flat areas on it and fell out on its own.
I bought the new ball on ebay specifically for the CB350 K4.

2. I have my new oversize by 1mm pistons ready to go the engineering shop with the barrels but I cant find any reference as to what clearance the engineer should bore to. Neither my Haynes manual or the CB250/350 FSM lists the clearance.
Plenty about the size of the piston but nothing showing bore measurements, even for standard pistons.
I had intended to just do the math between bore and piston size so I could advise the engineer. Page 41 ( pdf page) or actual page 30 of the FSM denotes.

I am told that Honda engines run closer tolerances so I want to get this right.
IMG_2100.jpg

Cheers

Gary
Auckland
NZ
 
The ball blocks off oil flow. It should be a tight fit.

I can’t speak thoughtfully to the piston clearance Q - the machine shop I use asks for the pistons rings and block and does the rest behind the curtains. Never had an issue.


- 1972 CL350
- 1985 VF700F
 
The best machinist I've ever had the pleasure of dealing with was also one third owner of one of the local Honda dealerships back in the day, and he turned out excellent work. He always set the piston clearance between .0015" and .002" depending on the intended use.
 
Thanks all for the fast answers!
I am relieved about the tight fitting of the rubber ball as I would have to split the bottom case off and redo it all again. Am I right then in assuming the ball is to close off an oilway orifice that was made during machining but not required to actually go anywhere?

AD thanks for the clearance values: the tighter one, .0015 , for normal street use and the looser one .002 for racing?

Gary
 
Also thanks to Mike for the link.
Some good discussion on clearance there and one guy is using the same pistons I have ( they look identical ) but sourced from Cruzinimage in Japan.
I will advise the Engineer to bore to .0015.
Gary
 
GaryJames said:
I will advise the Engineer to bore to .0015
Click to expand...

More accurately, bore and finish hone to .0015". If it's slightly over but still less than .002" you'll be fine. And yes, he typically set up cylinders intended for racing at the slightly bigger clearance knowing they wouldn't get a long break-in like a street bike might because back then none were liquid cooled. One of those opinions in that link was from our own CrazyPJ, longtime Honda tech and instructor at at least one motorcycle tech school.
 
Whilst I was for the engineer to bore and hone my barrels I am getting all the other small engine items done. Oil seals, Gear change shaft installed etc.
On the Left hand side, clutch operating mechanism, there is an operating arm which turns three caged balls to rotate on a profiled cam flange to lift the clutch plates via a rod that passes through one of the gear shafts. ( main shaft I think )
CMSNL drawing shows a ball bearing item # 21 described as a type 10. as part of this mechanism which the clutch rod presses on.
Although I bagged everything I seem to have misplaced this steel ball. I know it is important as I have one in the clutch operating mechanism on my 1946 Ariel!
I recall it being described elsewhere as a 5/16" ball.
Is this correct?

Second question is on CMSNL diagram for Upper Crank Case item number 4, outside front Studs seem to show a thickening about 1/3 of the way up each stud.
When you click on Item #4 down below the better picture shows something like a small band of something with some heat shrink over it.
When dissembling mine I found a small, maybe 1/4" long, what looked like electrical wire insulation on the front left stud only. It was split and easily fell off.
Do I need this? I assume it restricts oil flow down these two studs somewhat.

regards

Gary
Auckland
 
Searching this site I have discovered I am a victim of the non-oe gasket set barrel O ring scam!

can’t get the cylinder block to sit nicely on the upper rank case.
4287080C-D76E-4833-BDBC-3DBE23467528.jpg
so a now set ordered from DavidSilver UK. That will take some time to get to me.

also from searching around this site ( excellent information by the way ) I am struggling with getting the cam shaft installed correctly.
One thread tells me the little spigot on the end of the cam shaft timing side should be vertical and the cam lobes all pointing down.
with my little spigot pointing vertical the lobes are not pointing down.
A6521116-1169-4482-917A-8376EBFE3903.jpg
Have I read the advice wrong?
I know I have to pull the top end off again to fit the new barrel O rings but I thought I would go through the cam fitment for practice.

cheers
Gary
Auckland
 
I use the o-rings they put in the gasket sets all the time without issue. Make sure to clean the groove they sit in really well. I use Copper coat gasket spray on the base gasket, helps to keep it in place when manoeuvring the timing chain and rollers.

You need to use a stack of washers, larger nuts on at least two of the engine studs to pull the parts down tight before putting in the cam shaft etc.
 
Line on the cam gear needs to line up with the top of the cam box with the rotor at LT.

In order to fit the rest of the parts without damaging them the rotor is moved while holding the camshaft with tension on the timing chain until the pin on the camshaft is at 5 o'clock.

Being very organized with parts and tools is essential at this point .... having an extra set of hands can help .... I no longer ask SWMBO .... VBG
 
Nothing wrong with your cam, drive pin and left lobes are normal.
Set the pin at exactly vertical(top) and bolt the cam gear on with the rotor on the LT mark.
 
Re: the base gasket - if the o rings didn’t fit you’d know it when you installed them. They’d pinch and otherwise not want to sit in the groove.

The Honda ones are the only ones I’ve been able to get to fit with no issue, but manufacturing tolerances can have an occasional after market o-ring working.

Sometimes the knock pins (those little hollow cylinders you put in each level from the upper crankcase to the valve cover to keep everything aligned) can sometimes snag especially if everything isn’t perfectly clean, or you used raised jaw pliers to get them out in the first place and now there’s a small peak where material was displaced.

I’d check there first and give them a short go with light sandpaper, making sure each side of the hole they index to is squeaky clean.


- 1972 CL350
- 1985 VF700F
 
Thanks for the great comments and advice,

Have closely inspected the barrel bottoms and discovered an old O ring squashed into the groove, duh. I neglected to inspect this area when disassembling. It was below the surface.
my bag of discarded O rings and oil seals does not have the large O rings in it so I never removed them.
my non-oe O ring measures 2.3 mm in thickness , the Honda one is listed as 2mm.
I removed the squashed in one and installed the 2.3mm item pressed into the groove with a plastic spatula. This bit is tricky as it wants to rebound out. Pressing in equally around the circumference seemed to tame it.
I will put the cylinder block on tomorrow and report if it seats nicely on the upper crank case.
mean time I am still in anticipation of a small delivery from DavidSilver UK.
cheers

Gary
 
Sanity check please.
About to fit the clutch basket and oil pump back on the bike but I note the driving large ring end of the pump conrod that goes over an eccentric on the back of the clutch basket has a small proud flange, about 2mm high, one side and is flat on the other.
Inspecting the wear marks it looks to me that the flange side goes toward the rear of the clutch basket... to give some clearance when the basket is rotating?

My Haynes manual and the Honda FSM dont describe which way round it goes.

cheers

Gary
 
I believe you are correct. I just checked the FSMs we have and one copy is not clear enough to be sure, and the clearer copy is a darker scan that does not show the detail necessary to confirm. I don't have a 350 engine apart in my garage so someone else more familiar will have to verify.
 
Final Drive Sprocket .
After installing the sprocket I noticed some play, back and forth on the drive splines.
Took it back off to inspect but can't see any wear on the main output shaft splines or associated wear on the sprocket teeth either.
Added some grease but still seems too loose to me.
Nothing about this in either Haynes manual or the Honda FSM.

Cant post a .MOV video direct to VHT so link to Youtube:
https://www.youtube.com/shorts/euUlCvUMsfY

First time I have posted onto youtube... seems to work.

cheers

Gary
Auckland
 
It worked just fine. That's a bit more rotational movement than what might be typical, but they all have some movement both radially and axially, it's normal.
 
GaryJames said:
Thanks AD,
Since the cost for a new 16T sprocket is quite reasonable I think I will renew it.
The chain teeth on this one are in good shape too...pity as these are the normal wear points.

Price varies a lot but I found this on Fleabay:
https://www.ebay.com/itm/2219763755...WX5SF1jumszKMBvQofU3Y0dwfh|tkp:Bk9SR5D-wMSaYQ

Sorry, I don't know how to condense this link.

cheers

Gary
Click to expand...

Gary, don't worry about link lengths, the forum automatically condenses them. However, that doesn't appear to be the correct sprocket for your bike, check the fitment info they show below. Looks like a Euro version of the CB450SC in 350 size.
 
Yes, sorry, I posted the wrong link.
the one I have purchased is for a CB350. 16T as per:
https://www.ebay.com/itm/222258195526
JTF278.
not a bad price 8 GB pounds is NZD$13…approx.
postage to Akl NZ is about the same price as the Sprocket!
all up landed should be less than NZD$30…. USD$20….
cheers
Gary
 
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