75 CB360 - bad omen "yatagarasu" build

sav0r

Member
I used a very similar arrangement on my sub frame build. Though I put the hard point directly through the cross section of tube and gusseted the junction exactly like your model. I had the advantage of using a fairly large OD tube which made that possible though my build is in aluminum. Several thousand miles and 4 years later and it hasn't failed yet...
 

teazer

Active Member
DTT BOTM WINNER
That looks right now. Brace/gusset metal can be remarkably thin and stl be stiff & strong enough.
 

MiniatureNinja

Member
DTT BOTM WINNER
oh yea

and I got the pistons in and measured the deck with the cylinders installed - no gaskets. there is a .053" gap. I have a copper gasket from Lanni for the head, which is .042" which means I need .011" to get to "zero" deck - but Lanni only makes them as thin as .016

an "N.E." brand base gasket measures .020 but I can "squeeze it" with the caliper to get it to .0195
 

crazypj

Split personality, I fake being smart
Just realised your thread name is prophetic, you sure you don't want to call it 'lucky f****r' or something instead? ;D
You have one of the 'top' tolerance motors. ( or bottom tolerance?)
When I did my first 378 I skimmed 0.020" from block and head and still had clearance. Couple of 378 builds have had zero clearance even with a stock base gasket and been negative with skimmed block. Honda obviously was lying when they said what tolerances were being used (although, pretty sure they never gave a main bearing to crankcase or block deck measurement?)
It's added expense to have block skimmed but much easier to remove material than to add it back. Oh, just read post again, you need about 0.035"~0.040" between piston top and head, the 0.053" is how far piston sticks out at present?
As for shock mounts, you could probably run a 5mm drill all the way through using current threaded hole as guide then flip them over and drill 1/2"~3/4" to lighten them. Just be careful not to go too deep, about 1/2"~3/8" minimum to shoulder. Drill press will do it, I would use a pretty low speed and slow feed though (~300 rpm and 'feel' the cut)
Just had another thought to help with alignment. Counter bore for a short piece of conduit or similar, make mounts 'a solid bar' line everything up, weld in place, cut conduit and pull it out
 

MiniatureNinja

Member
DTT BOTM WINNER
crazypj said:
Just realised your thread name is prophetic, you sure you don't want to call it 'lucky f****r' or something instead? ;D
You have one of the 'top' tolerance motors. ( or bottom tolerance?)
When I did my first 378 I skimmed 0.020" from block and head and still had clearance. Couple of 378 builds have had zero clearance even with a stock base gasket and been negative with skimmed block. Honda obviously was lying when they said what tolerances were being used (although, pretty sure they never gave a main bearing to crankcase or block deck measurement?)
It's added expense to have block skimmed but much easier to remove material than to add it back. Oh, just read post again, you need about 0.035"~0.040" between piston top and head, the 0.053" is how far piston sticks out at present?
yes, .053" is how far the piston sticks out with no gaskets at all. so if I add the .042" headgasket, then they would stick about .011 past that...
 

crazypj

Split personality, I fake being smart
In that case you need ~0.047" base gasket to get 0.036" piston to head clearance, slightly thicker won't do any harm (there is at least one 378 where compression seems 'too high' when kickstarting)
You have 'low' motor
 

MiniatureNinja

Member
DTT BOTM WINNER
ok gotcha, so it looks like Lanni makes a .050 gasket thickness, should do it. by 'low' you mean the case is milled lower than average, so everything sits down further - causing the need for thicker gaskets?

the machine shop that did the boring of the cylinders did express some concern with the clearance numbers I gave him, saying that the higher compression may play some havoc with such tight clearances - I am 100% OK using higher octane gas as where I work I can get any flavor sunoco for cheap, and I do have the ol' electric leg for starting purposes

oh, and "Yatagarasu" is a mark of rebirth and rejuvenation (sorta what I am doing do this bike) and also a god of guidance, which I gladly accept from the many experienced members here!
 

540Nova

Member
Re: 75 CB360 - bad omen "yatagarasu" build

crazypj said:
In that case, welds are pretty good as it takes practice to make them pretty as well as strong.
Probably turn up amps slightly and turn down wire feed so you can burn in 'pretty welds' (you can work slower, I still remember the first time I used MIG, set up for 3/16" plate, I tried using on 1/16" sheet ;D )
I thought you were paying buggy makers to weld it. :-[
Ca. is a bit OTT with some hobby stuff, seems they only want 'professionals' with crazy amounts of extractors, scrubbers, etc to do 'anything' ($30,000 paint booth, etc)
I guess the DIY powder coating stuff from Harbor Freight isn't even available there?
There shouldn't be any volatile compounds with powder coat, unless you overheat parts as it's basically a thermosetting plastic 'covering' and the powder should be pretty inert? (although I'm sure someone can 'educate' me on the finer points?)
On a MIG, increasing wire feed increases amps. Perhaps you meant volts.

Sent from my SM-G955U using Tapatalk
 

crazypj

Split personality, I fake being smart
The piston clearance is fine, it isn't s 50 yr old V-8.
The '0.001" per inch of bore' is so outdated it isn't even funny anymore
If you were using Wiseco you would need more clearance as they use quite a soft, high expansion alloy.
What surface finish did they put on it? I usually finish wit 400 grit hone and rarely bother with Flex Hone as 'extra' step.
Had one on dyno @12,000 rpm about 1hr after building motor, only got 2 'heat cycles before being beat on
Even in 70's Suzuki (and most others) were using higher quality high silicon alloy 'low expansion' pistons. I hesitate to say it, but, if you want some idea how strong they are, stand one on a flat surface and hit it with the biggest hammer you can find -14lb sledge hammer will work (basically what happens when you get pre-ignition or detonation) Will probably dent top but overall dimensions will be relatively unchanged. You won't need anything better than 93 octane, I think if you check with other 378 owners, 87~89 still works fine
 

crazypj

Split personality, I fake being smart
Me too, sometimes put some 91 or 93 in but only if I know I'm going to be 'more stupid' than usual chasing 900's (it gets 87 on the way home ;D )
 

MiniatureNinja

Member
DTT BOTM WINNER
do you think with the oil transfer piece opened up a little, the center cam 'bearing' drilled for oil that I could reach 10-11k rpm intermittently without too much issue?

I know the points is a limiting factor... but I have a hard time going with pamco electrics on this bike I've heard they just arent reliable
 

crazypj

Split personality, I fake being smart
Points are designed to 'bounce' around 11~11,500 rpm, you can use an oil-stone to change points cam profile slightly so it will rev higher but I haven't bothered since around 1975 ish. The other thing people did was 'double spring' thhem using extra spring from old points set.
If it was a race motor it could be worthwhile swapping ignition system but points ain't too much of a chore unless your riding every day when 1,500 miles comes around quite quick
The oil transfer piece mod is the best mod I've come up with for CB/CJ 250/360. Extra oil hole into journal is also a good idea if cam isn't 'gun drilled'. I consider myself personally responsible for the 'price hike' on 360's, If I hadn't figured out a way to make them more reliable they would still be cheap 'unreliable junk' prone to seizing cam bearings ;D The cam bearing is really the only issue with t.he motor, generator output is low and reg/rect is 70's technology but both are easily fixed
I have never had a crank or transmission fail (even with the heavy Suzuki GS1000 pistons, 391cc and 10,000+rpm)
That bike even got me on TV as I was having so much fun (still got another 14.48 to go for my '15 minutes of fame' ;D )
 

MiniatureNinja

Member
DTT BOTM WINNER
I've only ever seen one CB360 in person - and where I am there are a TON of vintage bikes (mostly BMW R series and triumphs, harleys) there is a vintage bike meet every month at the local taco joint... even last summer people loved my CB360 so many 'old' guys reminiscing about their trips up the coast back in the 70s with their own CB360. Few people recognize it unless they've owned one and when I'm done with it this spring I'll love to talk about all the little details that went into it. Maybe have to make a [ THNX PJ ] custom cali licence plate!
 

crazypj

Split personality, I fake being smart
Except for polishing one vacuum screw, carbs are done.
Because the screws to mounting plate ha been loose I had to flatten the plate back with some 220 on surface plate. Did tops an carb bodies, they were actually pretty good compared to a lot I've done in the past. I polished mounting plate, it's kinda a 'trademark' ;D
 

Attachments

MiniatureNinja

Member
DTT BOTM WINNER
looks awesome PJ! paypal incoming!

now I can't WAIT to get this thing back on the road

I ordered an .050 base gasket today
checking pisting ring gaps today

gotta finish drilling the clutch basket (holes drilled, just need to "smooth" them

also, tomorrow is fabrication day (welding wednesdays) so redoing the rear end. and then looking at possibly hiding the battery and electronics under the tank. I didn't do this before because no room with the coils, but since coils are gone I can make it work I think.
 

crazypj

Split personality, I fake being smart
Don't put battery under tank, it gets too hot and will 'kill' it.
Mount under front of swing arm behind engine, it's pretty well hidden plus you have various bit's there from centre stand to hang brackets off. You can also direct heat away from it to a certain extent and if it does catch fire you won't have a bomb
0.050" gasket will put you right where you need at 0.039" 'bump' This should be a quick motor even with stock cam (around 120 on a good day)
Almost forgot, I put 110 and 120 jets in a baggie, you have 115 fitted at present, may be a little rich, you'll need some plug chops to find out. Fuel screw is set at 1.5 turns out, will probably need adjusting? Anywhere between 3/4 and 3 turns is 'normal', less than 1/2 turn needs smaller pilot (I modified the pilots to Kei-Hin spec, didn't touch the new ones so you have options if you like playing carburettors ;D )
Be very very careful launching over 7k, it's so short and light things get very 'interesting' ;) (at least to 50~60mph )
 

MiniatureNinja

Member
DTT BOTM WINNER
crazypj said:
Don't put battery under tank, it gets too hot and will 'kill' it.
Mount under front of swing arm behind engine, it's pretty well hidden plus you have various bit's there from centre stand to hang brackets off. You can also direct heat away from it to a certain extent and if it does catch fire you won't have a bomb
well I planned to "shield" it and put heat reflective tape - the rear of the exhaust will be much closer to that area

but I already caught fire on this thing once... so I guess I'll just go back to my original idea and mount it under the seat
 

crazypj

Split personality, I fake being smart
I edited previous post.
Exhaust is way to short if it's exiting around swing arm pivot point, your not going to run open pipes (could be interesting with 125~130 secondary mains on a dyno to see just what it can do) I would guess around 41~42bhp at te wheel (compared to 36 at the crank that Honda claimed)
CB350's dyno around 26~28bhp, 360's 24~30 at the wheel (obviously more production variations on 360)
 
Top Bottom