CB360 project

Doh, I forgot they were already settled, that's why you had them skimmed ;D
Set to 0.038"~0.040" it will be pretty impressive when run in.
I think it's geared for 127mph @ 10,000rpm, 120 should be 'easy'?
Brendon has 'run away' from a 'new' Triumph Bonneville on his 378
The guy had messed with fuel maps after fitting new exhaust so it wasn't running right but even so, it shouldn't be slower than a 40yr old CB360 8)
 
We've got a joker. Ha. I'm no machinist so I go along with what people tell me. Are you referring to head gasket thickness?


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I think my gasket is .042" so that minus the .004" off the head would make .038". Fair enough


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What size base gaskets are you guys running? I'll measure for proper thickness of course but it's nice to have something to compare to


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I don't know if the variations are on the crankcase top or cylinder length but there seems to be a variation. (I think it's crankcase as blocks I've measured are all very close)
I'm running a 0.060" head gasket on one motor and 0.040" on another.
The original had 0.040" which is why I recommended it, the other motor wasn't built for a long time so I didn't realise they were different from 1974 to 1975>
 
When I dry fit everything to get base gasket thickness, should I remove the rings from the pistons? Or just leave them on? I don't want to risk breaking them but I also don't want to scratch the cylinders. Which is the lesser of the 2 evils?


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My measurements are coming in between .047" and .051" at the wrist pins so I guess I'll be ordering a .050" base gasket from Lani.

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Measured the base gasket I had on there and it came in at about .018" so that wasn't helping me much at all.

I double checked that the cylinder positioning dowels weren't preventing the cylinders to sit right down flat on the case.

And checked that the head positioning dowels wouldn't do the same. It looks like the head doesn't sit flat just because of the rubber seals around the 2 rear dowels. I assume that's normal and that they'll compress when the studs are torqued down to form a tight seal.

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Check there isn't any sealer inside the holes for seals, it can cause them to sit proud. They will compress to form a good seal. (better than stock with the 0.008" or so you removed to get things flat) You are using new ones? (not that old ones make much difference if still 'squishy')
I would put couple of old gudgeon (piston) pins on studs, clamp down block, lock crank at TDC and measure how much pistons are sticking up.
Use that measurement in combination with the head gasket you already have to get close to 0.038" clearance.
You may need to grind dowels a bit shorter, check depth of hole both sides, add and measure dowel length to compare. There is a possibility they are slightly too long , maybe from a different motor or manufacturer?
I have seen it a couple of times with head gasket leaks, always the last thing you think of before patience finally disappears ;) (just walk away, walk away ;D )
Anything I post at present will be about head and base gaskets.
 
thrillseeker said:
what is the 0.038" clearance between?
Click to expand...

Between piston and head, the 'squish' area (aka quench for car engines)
You'll need some 'clay' (plasticine or playdoe?) and check the 'angled' area of head compared to crown of piston. Use a 'wet' razor blade to cut through 'clay'
Put a dusting of talc on 'clay' so it doesn't stick to head
 
Dowels are fine. I removed the rubber seals and the head sits flat. Will check squish area when I get back from ny next week.

To clarify:
1. Install cylinders w/o base gasket
2. Install head gasket
3. Put clay on piston
4. Install head w/o cam and snug down with a couple nuts
5. Rotate crank through tdc
6. Remove head
7. Cut and measure clay on angled portion of head
8. Subtract 0.038" from that measurement to get ideal base gasket thickness
9. Order base gasket with thickness closest to ideal thickness.
10. Party on

Should I measure both sides?


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thrillseeker said:
Dowels are fine. I removed the rubber seals and the head sits flat. Will check squish area when I get back from ny next week.

To clarify:
1. Install cylinders w/o base gasket
2. Install head gasket
3. Put clay on piston
4. Install head w/o cam and snug down with a couple nuts
5. Rotate crank through tdc
6. Remove head
7. Cut and measure clay on angled portion of head
8. Subtract 0.038" from that measurement to get ideal base gasket thickness
9. Order base gasket with thickness closest to ideal thickness.
10. Party on

Should I measure both sides?


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Click to expand...

There is a chance the motor won't turn over without any base gasket in place?
It's easier to just measure exactly how far piston is sticking up from top of cylinder to get correct clearance.
You then 'clay' piston to verify it's correct.
You could also use a couple of base gaskets to get clearance. As long as they are in reasonable condition you can measure them with mic or caliper. You may need to add to the thickness to get correct clearance?

I used to do all piston to head clearances, inline 4 takes a little longer but shows if combustion chambers need modifying.
If they are already modified you should only need to do one.
 
So it sounds like as long as I get a base gasket that brings the pistons level with the cylinders I should be damn close to 0.038" since I already have a head gasket that's 0.042" and had about 0.004" milled off the head. Correct?


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She's a runner! Got the motor back together, valves, cam chain, and carbs adjusted and synced, pamco ignition installed, timed, and fueled!

Took a short ride and she was poppin like crazy at me and the rear brake had too much travel. so I adjusted idle mix screws and re-synced the carbs.

Went for another ride and noticed the regulator was really hot so I relocated it to the bottom side of the seat tray so it gets more air.

Going to get it registered and take baby steps going longer distances. She pulls like crazy! I haven't even tried full throttle yet.

Also, she starts on one or two easy kicks every time!


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Sitting pretty in the garage along with my new project I picked up. 74 ST90. Already started taking it apart. Carbs are currently taking a bath and the gas tank is de-rusting.

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LOL, now you know why 22cc is totally out of proportion to the power increase and is totally worth the aggravation getting it set up 8)
 
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