Possibly entering the 378 club!

70mm pistons arrived from Japan in less than a week!

Off to the machine shop today
 

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MiniatureNinja said:
WHAT?!?!?! I've been scouring the Ebay for months for one of those!! :(

As annoying as it is, you have to get them as soon as they post. I got mine within 20 minutes of the listing being posted.
 
They never stopped CJ cam bearings failing so it's only needed if you don't ever check oil level plus park on side stand on highly cambered roads and leave bike idling for extended period. It would probably be easier to weld over the original pick up and extend it into center of case or even just make a complete new pick up?
 
crazypj said:
They never stopped CJ cam bearings failing so it's only needed if you don't ever check oil level plus park on side stand on highly cambered roads and leave bike idling for extended period. It would probably be easier to weld over the original pick up and extend it into center of case or even just make a complete new pick up?

I have a spare CB pickup, so I may take that up and make a modified one. I am meticulous about checking proper level and change intervals because I know how important that is to engine life for anything (plus being a former Marine has taught me that equipment maintenance is key to survival)
 
I’m a little jubious that the pickup will be genuine CJ..... lets see what turns up!

Meantime i’ve done the oil mods, and taken the pistons and barells to the shop

Also contacted CopperGaskets to line them up for base and head.

I’m awaiting a gasket kit and viton valve seals, the ones in the old kit i have seem crap, then i think i’m ready to assemble.

Will post pics when stuff arrives.

Steve
 
Well the ‘NOS CJ360 Oil Pickup’ arrived, and yes it’s genuinely not the same as the CB360 one, and looking unised and a bit rusty!

I shall clean it up and install.

With the pressure relief mod, clean oil pump, drilled clutch basket and oil ways drilled out to 2.5mm ( they were 2mm) i think im ready to button up the right case?

Steve
 

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Yes, hd springs installed.

Ps, there’s another cj360 pickup listed on abay by the same seller.....

Steve
 
Collected barrels and pistons from the machine shop this morning, and so couldnt wait to test fit and measure up for gaskets!

With a new base gasket in place and the barrels bolted down i’m seeing :

Pistons sticking up .045 from the barrels
Base gasket measuring 0.018

So if i went for a base gasket at 0.063 from Lani then i’d have pistons perfectly flush with the barrels.

A 0.042 head gasket would then give me clearance of 0.42.

Is this correct and the right approach?

Steve
 

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Yep, numbers work out
Did you check gasket after it was compressed? I doubt if it would be more than 0.001" but it's generally easier to clamp cylinder down without gaskets then work out what combination will get you closest to 0.040" clearance. Having thickest gasket on base is a real good idea as there is way less pressure 'down there'. ;D I'm really interested to see how a 70mm bore turns out. When I did my CJ250 to 70mm I used GS1000 pistons and flycut the head. Using stock 360 head gives a different combustion chamber shape and probably volume? I was actually on TV with it in 1995 (or 6?) There was an event at LLandow Circuit with a RWYB 'sprint' Thanks to the 'magic' of television, I was filmed during a run then it was cut into the Welsh Champion drag racer doing a huge wheelie off the line making it look like I was 'winning (even though filmed on different days) only another 14 mins, 55sec to get my full '15 minutes of fame' ;D
 
Thanks both.

I did measure base gasket after removing it, so had been compressed.

I’ll order the copper gaskets and hopefully get rebuilding soon!

I’m a little unsure on piston rings.

I have a three part oil control ring, being two thin rings and a ‘wavy’ centre, and two thicker compression rings.
Both compression rings are stamped ‘100’ on what i think is their upper face. One ring is black edged and one silver.

Have you seen this before?, i’ve not take a picture yet nor contacted the seller.

Steve
 
Rings are completely normal, marked as 1.00mm oversize. Expander ring goes in between side rails. Make sure ends are butted and not overlapping (sometimes they look 'too tight' assembled correctly) Side rsails don't haver up or down face
Top ring is chrome face, second ring is 'black'
Numbers up.
Oh, stagger the oil ring rails and have gaps 'opposite' the 'join' on expander,(I only go about 1/2" either way) it only makes a tiny difference but can seal 'better'.
 
Gaskets ordered from Lani at Coppergaskets, he was very prompt in responding and in making and posting the gaskets too!

While i wait for those to arrive i’ve painted the head and barrels, and built the head back up with new Viton seals.

Cant wait for the gaskets to arrive so i can rebuild and fire up the CB389
 

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Moving right along there. I had quite a bit less meat on my build, and that's what I did went with a thicker base gasket. You could probably get away with shaving some off the case but gaskets is more reasonable solution.
Factory valves and guides?

Sent from my SM-G955U using DO THE TON mobile app
 
Stock valve guides are actually real good. It's only if you fit oversize stainless valves the guides need changing (something they don't tell you when you buy stainless steel valves, the stemscan gall in cast iron and need bronze guides) Really though, it isn't worth the extra expense of oversize exhaust valves but the+1 (35mm) intakes will make all the port work better as it's already oversize.With a '390' is should be good to 'cruise' around 85~90 with top end around 120 on stock gearing (17/34) I got confused the other day with the CB550 591cc 'kit' and 70mm 389.46cc of 360 (35x35x3.14159x50.6x2 = 389.4629)
 
Gaskets and new dowells arrived in the week so guess what i’m doing this weekend
 

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