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Discussion Starter · #1 ·
So I finally got here.
going to start putting some info on the 378cc conversion I'm doing on 1974 CB360.
I'm building two bikes which will be similar but not the same ( one is getting all the frame brackets removed plus modifications to clutch cover to run external cooler and filter)
They are both running Suzuki GS850 pistons which seem to be a direct replacement (and 3mm oversize :lol: )
Quite a bit of stuff got lost when hard drive died (still trying disc recovery software to see what I can ge back-doesn't look good so far)
I put quite a few pictures on photobucket and some are still on camera memory card.
may take a couple of weeks for me to find time to get everything on here
Last pic is modified clutch hub, extra oil flow helps to cool plates.
Put both dyno runs up, first is with MAC pipes, second with with new exhaust system I made.
Its running really, really rich (10:1 fuel air ratio) going to down jet and try to get another run sometime. I 'lost' almost 3hp from the open exhaust/original numbers
somewhere new to bore people with my CB378 and XS650 Yamaha stuff.
link to the 378 I'm building
And the link to SOHC4 in case you missed it
http://forums.sohc4.net/index.php?topic=30210.0
:lol:
Will start posting when I have more time.
PJ

I've edited the 'me again' post, removed pictures and put link to this one, just in case anyone finds it in the future

http://s91.photobucket.com/albums/k315/ ... a%20CB360/






 

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Sensei
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... I assume putting the forks on backwards was deliberate......
Love the muffler, Where did you find it?....
Steve
 

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Discussion Starter · #3 ·
Its a 2" Thrush straight through glass pack painted black.
Would have been too recognizable if I left it red :lol:
Forks were reversed for two reasons, it makes brakes more effective (there is now a 'servo' action as caliper mount try's to rotate on pivot)
Weight of caliper behind fork leg changes steering slightly
PJ
Edit, its an inch and three quarter Thrush Glass pack, not 2"
 

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PJ, (Not for the sake of arguement, but)... Moving the positioning any unsprung weight has little to no effect on tractability or steering. This is an "urban legend"....Reducing unsprung weight will.....OR, .... Moving sprung weight (especially moving it nearer to the center of gravity) WILL affect the "handling" properties...... Also, The caliper carry-arm pivots side-to-side, Not vertically or rotationally... (This remains the same whether in front of or behind the fork leg).... Flipping the forks ONLY makes them harder to fully drain when changing oil...... Having the calipers behind the forks, up-side down or any other positioning does NOT affect how well they function, Nor the amount or direction of the forces exerted upon the forks... (hence the forces transferred to the bike in general)... Having Both brakes on the right side may "seem" or "feel" different when turning and braking simultaneously, but that's about the total effect (mechanically, the construction of the wheel places all braking force evenly across the axle (on the bike side) and towards the center, bottom (from the tire's standpoint)...... However (and barring refuting evidence) if you believe it works for you, go for it!
 

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Discussion Starter · #5 ·
oops,
the Thrush is a 1.75" and I did have to do a bit of hunting around to find one that small diameter.
The pivot point is not directly above rotor center line (its 'inboard' by about 6mm)
The caliper rotates 'off center' so when brake is applied it does have an effect.
When caliper is in front of the fork leg its 'dragging' and applies pretty much equal pressure.
I first did this on my 550 in 1978 or 79.
You do get better brake feel but it does wear pads out quicker, probably because you can leave braking much later (around 4~5000 miles a set of four pads for dual disc set up)
The 'fixed' pad appears to wear quicker hough,.
I keep the adjuster screw/spring in place so fixed pad isn't touching rotor when brake is 'off' (which means the wear isn't caused by constant rubbing-that just tends to glaze pads and make brake squeal)
I have tried both set ups and prefer feel of caliper behind fork leg.
From an engineering standpoint the forces may well appear equal, but from experience it does feel different and works for me. (and I can use a shorter flexible line directly into caliper :mrgreen: )
Also, as you say, it moves weight of caliper behind axle instead of directly over it.
Although the mass is closer to center and slightly lower I'm not sure how it affects handling?
I had no problems with duals on 550 (Honda rotors are not as heavy as Yamaha ones but still not lightweight)
I'm not expecting any issues with smaller lighter rotor on 360
PJ
 

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Discussion Starter · #6 ·
Doh, I forgot I already posted this , thought the pictures had gone missing.
now its up twice.
Should I delete the one with the pics? viewtopic.php?f=5&t=177
PJ
 

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Sensei
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PJ....I understand "feel" and if that "feels" like it is working better, by all means.... However, the reason it "feels" like it is gripping better is that the "pivot" (the center point of the triangle described by the three bolts where the carry arm mounts to the forks) is now higher off the ground...This creates a longer theoretical lever length (the length of the vector line from tire contact center on the ground to that triangle's center) thus transferring more "feel" upwards through the forks to the rider (better input)....However, the caliper sits EXACTLY at the same distance from the axle with either set-up..... This length (essentially rotor radius) is the determinant for the amount of actual "leverage" force applied to the rotor... If your "carry-arms" are flexing that is a PROBLEM... They shouldn't... ( although most "bracing" resists "push" {compression}to a lessor extent than it resists "pull")... The shorter wear times are most likely due to the fact that the rotor is spinning faster/longer and the brakes must be applied harder during "late breaking" .......... The brakes don't work any better, they just allow you to feel how well (or not) they are gripping and control them better.... I too prefer the "better rider input" scenario...... Just wanted you to understand WHY it "feels" better......... Steve
 

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Never heard about improved braking (or braking feel) by mounting the calipers behind the fork legs, but I've certainly read about improved steering (or steering feel) by doing it.

The pivot point, or steering axis, in steering is the steering neck. When the calipers are out front of the forks, they are further away from that axis. You can visualize the steering effort with a heavy mass further away from the axis. Quite a bit of effort to swing those heavy calipers back and forth when they're way out front.

With the calipers behind the forks, they're closer to that steering axis. Much less effort involved to swing those calipers back and forth when they're close in like that.

Interesting discussion, and nice bike.

I really like the looks of that Thrush muffler. Very British pea-shooter.... I'm going to have to remember that one... My only nit to pick would be to install some less obtrusive hanger bracket - say, a welded bracket bolted to the passenger peg mount.

Good job!
 

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Discussion Starter · #9 ·
Hi kirkn,
The hanger was just something I slapped on so I could get a dyno run done in work at short notice. (happens every 6~7 months)
Its going to stay as a clamp on around silencer body, welding will probably destroy the packing. (and its not re-packable)
The drop arm is probably going to be fabricated from 1/2" tube (cos Honda used to make them that way on race bikes)
I have a rather neat solution for rear-set rear brake (well, I think so) the bungy cord return spring on bent footbrake lever is only to allow bike to be 'tested', its leaving when I get carburation sorted out
The passenger peg mount is where rearset is mounted, I have a second bracket going there to stabilise pipe, its too far forward to support silencer
I'll put pics up when I've done it
PJ
 

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Discussion Starter · #10 ·
Forgot to mention, the feel of brake only works with swinging calipers on earlier Honda's, the sliding or twin piston calipers don't feel any different during braking if they are in front or behind fork legs, they do feel different cornering though.
I have seen Kawasaki's with calipers bolted to front of fork leg 'lose' the mounting 'bracket' when the alloy fails. (its nasty when caliper goes around with disc and hits back of forks, then falls into wheel)
PJ
 

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Discussion Starter · #11 ·
Got jets swapped,#58 drill, 0.042" dia drilled out the stock 100.
Connected up charging system, (just connected from generator to rectifier to voltage regulator to battery) its got battery up to 13.2V (from about 12V)
Did compression check, right 210psi, left 208, would probably have been higher if I hadn't been revving it to 11,500 (and, if I had fitted new rings when I built it)
Its way above Honda recommended 175~185psi though, its definitely going to need good gas :lol: :lol:
sort of ready for dyno run next week.

PJ
 

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crazypj said:
Did compression check, right 210psi, left 208, would probably have been higher if I hadn't been revving it to 11,500 (and, if I had fitted new rings when I built it)
Its way above Honda recommended 175~185psi though, its definitely going to need good gas :lol: :lol:
sort of ready for dyno run next week.

PJ

From the applicable page of the Honda 360 Maunual -

 

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Discussion Starter · #13 ·
Re: Hi'yall-CB378 conversion

Cool, lower than I (almost) remembered.
I know it isn't carbon build up, only have about 10~30 miles since top end re-build
Could you check float height spec?
I keep finding 19mm for brass floats, the plastic ones are set at 19mm, I think its right but would like confirmation if possible.
Thanks,
PJ
 

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Here's the Honda Manual - download it, you should have it if you have the bike.
The float levels are listed in it. Just offhand, 19mm doesn't sound too far off - but don't take my word, check for yourself.

As for the compression, the gauge you're using could be in error. They're not Nat'l. Bureau of Standards tools or anything, so it could be off.

http://home.comcast.net/~tbpmusic3/Honda_CB250_CB360_CL360_CJ250T_CJ360T_Shop_Manual.pdf
 

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Discussion Starter · #15 ·
I looked it up, 18.5mm - 3/4" which is actually 19.05mm?
PJ
 

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Discussion Starter · #16 ·
Got couple of dyno runs today, still running rich but a lot better than it was.
Clutch is now slipping, got printout showing 40.38bhp peaks,(@about 11,500 rpm) realistically its closer to 35bhp (@9,000) but there will be more to come when I get carbs sorted.
The 107 was too small.
I drilled main jets #56 drill, (works out 116.5) I'm pretty sure 112.5 would be perfect.
The other problem, needles are non adjustable and they need to be lowered.
Mixture gets pretty rich around 5~6,000rpm (transition on needle jet when slide starts lifting)
Needle need dropping but as its fixed I think I have an alternative method.
I've posted scan of single roll on run, better for mixture setting. Also posted some explanation so you have an idea what your looking at

PJ
 

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Discussion Starter · #17 ·
Spent most of day working on Yamaha XS800. Made a rev counter drive plug this evening ( actually made a couple :roll: )
Managed to get measurements backwards on first one so screw recess was in wrong place. Not a problem though, just machined the flange off so it fitted into the cam box slightly recessed :lol:
Here's pic of MkI and MKII version, I'm liking the MKI failure better
PJ
Clickable link to XS800

MKI

MKII version
 

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Discussion Starter · #18 ·

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The way you mounted that speedo looks GREAT! Super clean and pretty much what the factory should've made it look like.

GB :mrgreen:
 

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Discussion Starter · #20 ·
Did a dumb thing last Saturday, bought an early Pontiac 389 engine because it was cheap on Craig's List. (less than $200.00)
Its older than I would like but just a block was getting into several hundred+
It came out of a 1965 Catalina.
I've been looking for a 400 motor to rebuild for 76 Firebird but this turned up.
Its a large heavy chunk of cast iron :D
Only plans for now are to strip it down and get it cleaned up
PJ
 

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