Honda 360 Engine Build - +2mm Bore + Cam

OK... so my engine build is pretty much done at its current stage, so this thread is mostly for posterity. I'll be focusing mainly on the technical, but I'll be happy to answer any questions on the aesthetic (should they arise).

Goals:
*Repair Cooked Top End
*Increased Power
*Higher Redline
*Hitting "The Ton"
*Fun and Learning

Changes to Engine:
*+2mm bore (356cc to 378cc) done at the local machinist
*Custom Forged Pistons from Arias (Compression from 9.5:1 to 10:1 and 11g lighter than stock despite being +2mm larger in diameter)
*Megacycle cam (duration from 221° to 251° and lift from .341" to .382")
*R-D Valve Springs with Aluminum Caps
*Steel Dragon Velocity Stacks (tuned for 5th wave at 10,000 RPM)
*Custom Copper Head Gasket from Copper Gaskets Unlimited
*Front sprocket upped from 16t to 18t
*Stiffer Clutch Springs from Dennis Kirk
*Stainless Steel Caphead Engine Bolt set from eBay (seller: alloyboltz)
*New Gaskets All Around
*Tachometer Cable Blockoff from our own crazypj
*Hondaman Transistorized Ignition Assist Unit
*Oil galleys from the crank case to the head drilled out slightly (13/64" maybe?)
*Removal of stock 2:1 exhaust and switch to a set of stock CB360 2:2 headers
*Spark Plugs (TBD, but hoping to find a dual electrode set set with the specs I need)
*Jetting (TBD)

Early in October of 2010, I was riding into work when the bike started making some funny noises. I pulled into my parking space and there was some white smoke coming out of the breather. I immediately shut everything off and checked the oil level. The dipstick couldn't find any. At lunch time, I came back out and gave the ol' girl a kick and everything turned over OK so I picked up a quart of oil and added it in. I made it home OK but things were not sounding good™.

I let the bike sit for a couple of weeks without riding it until I made the decision to just tear it apart and restore it from the ground up. This led to my desire to café it and you can follow my full thread here. This thread will focus on the engine.

Here's how things looked straight off of the bike:


As you can see, I had an oil leak coming from the head gasket (which was the probable cause for my oil starvation issue) and a lot of metal dust under the sprocket cover (cause still unsure, but I'm going to attribute it to poor chain lubrication).

After opening the rocker cover, I could immediately see that the rocker arms on the left side had been eaten up. The lack of oil led to too much heat and there was significant scoring on the followers and the cam. Luckily the journals were OK and the coking came off with a bit of 800 grit paper.



The dark black streaks on the cam lobes in this pic and next indicate it's time for a new one:





The combustion chambers look OK, but the darker combustion on the left chamber is a possible indication of running rich. In my case, I had oil leaking from the head gasket and into the cylinder a bit at a time.



Just a quick shot of the inside of the cylinders with the head off:



Engine finally disassembled after a rubber mallet and a blow torch finally loosened the jugs from the upper case:



Inside of the cylinders and the skirt of the pistons all looked good with limited wear. Everything measured in spec but at this point I had already decided to replace the cam with an aftermarket part that would require deeper valve pockets. The piston cost for increased compression and larger bore was negligible and so I decided to go for it.





A couple of more pics of the rocker arm damage:





Now that all of the engine was taken apart and cleaned up, it was time to do the carbs. I disassembled everything and dumped all the parts (excepting the diaphragms) into a gallon of pure lemon juice and then proceeded to boil them for 15 minutes. Man, alive! That is a FUNKY smell. I also had the joy of boiling them over and burning lemon juice onto the top of the stove... The Mrs loved that.



Here's everything after the lemon juice bath. Boiled lemon juice has worked better than anything else I've tried and would definitely do it again.



Next, the carbs went back together again. I used some small caphead screws in the diaphragm cover and bowls to replace the stock JIS ones. While I was there, I fixed the choke (PO had the lever on wrong and the butterfly valves in backwards).



Sometime later, my refurbished cam finally arrived in the mail!!!





Followed shortly by my new pistons:



New springs from R-D came in a bit later:



Followed by velocity stacks from Steel Dragon Performance:





While waiting for parts to arrive, I got some painting done on various engine bits, including the cases. Nothing special here, just some Rustoleum Metallic Enamel which will later be clear-coated with some 2K urethane.





The engine is starting to go back together now. Up first, I reassembled the head with the new valve springs and retainers. As you can see in the pic below, the valve stem now sits a bit above the retainer. I was assured (after double-checking) with the manufacturer that this is by design and all the clearances checked out.



After that, the bottom end started going together. I made sure to use clean towels on the workbench to avoid screwing up the paint any more than necessary. Yes, I am missing one of the gears on the shaft. No, I didn't realize it until I had everything put together.



New piston at TDC:



After getting the bottom end sorted out correctly, it was time to check clearances for the new cam and pistons. A chunk of modeling clay laid across the top of each piston prior to reassembly will let me know all is good:



After assembling the engine and turning it over a few times, I took the head back off to examine the clay. Looks like the valves didn't "cut" all the way through and so we're OK (that tear on the right side was caused by me, bending the clay back. Ignore it.)



Then I had the fun of getting an 18t sprocket to fit in place of the original 16t. The 18t sprocket fit onto the countershaft OK, but it was too wide to secure using the stock clip. Not having access to any milling equipment, I decided to take a bench grinder to it and used a steel straight edge to check my progress. The fine adjustments were made using a die grinder with a 60 grit sanding wheel attached. Final fit is close and I'll have to keep the chain tight to avoid eating up the guard under the sprocket cover.







The engine is now sitting reassembled and (as of this date) still waiting to be fired up:





I've since got the engine into the bike and adjusting the valve lash and timing. I went with spec on the tappet to valve clearances but decided to go with an addition 3° of advance. The reason being is that the cam, having more overlap, may induce some tougher starting if the spark doesn't fire soon enough. I will probably have to/want to retard the advancer an equal amount.

After I get this thing dialed in, I'm (optimistically) expecting a gain of around 10 peak hp; an increase of about 1/3. Most of that comes at the expensive of moving the power band up to the higher RPMs due to increased duration of the camshaft. Under 3,000 RPM I'm expecting to lose about a 1/3 of the power I had before. That, coupled with my gearing changes, may make the bike a bit of a pig at low speed. I'm hoping that first gear is low enough to pull through it though and I'll just keep it above 3,000 RPM the rest of the time. I'll only know for sure once I get her on the road. Provided things don't work out as planned, I can also drop a few teeth on the front sprocket and/or up the teeth on the rear until I get a decent feel.

Estimated top speed is around 115. Maybe 120 after I make some further modifications...

Things I would have done differently (or things I would still do the same, but probably shouldn't):
*Made use of used rocker arms with new cam
*Didn't remember to match up rocker arm pins with the specific arm from which they were originally pairs
*Forgot to measure thickness/warpage specs on the clutch plates before reassembly
*Had the inside (possibly outside, too) of the cases professionally cleaned and/or blasted
*Had the new valve spring strength tested to ensure proper strength

Possible list of future modifications which I am planning (and will update this thread if/when I get around to it):
*Skimming the head and slotting the cam gear for additional compression
*Electronic ignition
*External oil pump + cooler
*Remove casting marks and polish the rockers, conn rods, and crank
*Mill/grind gear edges to cut down on rotational masses
*Fuel Injection?

Lol fuel injection.

mmm. fuel injection. I've looked into it. Pain to set up at first, but once set up, is just awesome.

beautiful work! beautiful motor. love it.

Sonreir, you're inspiring me. I'm doing a bit of this too, and using a lot of the same parts. I'm shooting more for low end grunt though:


2mm overbore

GS850 pistons
Cam modded and external oil line tapped into engine; courtesy of PJ
Carbs modded courtesy of PJ
Copper head gasket, same as yours.
Stiff clutch springs, same as yours.
Bolt kit, same as yours.
All new gasket kit, same as yours.
Remove all electric start components.
Possible starter block off plug, courtesy of PJ
Tach block off plug, courtesy of PJ
Electronic Tach
Hondaman Ignition
XS650 coils
Decked head
Slotted cam gear
Bronze cam journals (mine are ate up)
Reground and hardened rocker arms.
Battery eliminator.
Combined regulator/rectifier from Oregon Motorcycle Parts


Everything is getting soda blasted, and when i add an external line I might add an oil cooler and filter as well.






Theres an old writeup online about someone doing a CB350 engine with a CBR600 stator/rotor for charging, throttle bodies for injection, and megasquirt control. Looks like you might be able to make it work for your fuel injection plans.


Great job man!

oh sonreir... forgot to mention. are you fitting a thinner base gasket? your piston seems a little low in the bore.

what kind of retainers are you running? also, are your rocker faces and cam lobes hardcoated? running higher pressure springs as well as higher lift cam in that top end is likely to destroy the engine again unless the oil issues are thoroughly resolved, hardfacing both cam and rocker arms will help a little


also, instead of using clay, try some solder, you can measure the clearance with a caliper that way, with the clay the way you have it, it's not telling you much, the fact that the valves didn't actually contact the piston at room temperature and 0 rpm doesn't say much about how close they'll be during running conditions... you also want to measure the piston to combustion chamber clearance, around the squish band, because the engine studs are cooler than the conrod and piston, the piston will get closer to the chamber as the engine gets hotter... you've got a lot of expensive parts in an engine that was imho a shitty design from the beginning, so you want to be extra careful not to get them destroyed

[quote author=B L A K E]Lol fuel injection.[/quote]

It's doable. I'd need a new rotor and stator to generate the juice for a fuel pump and electronics and then I'd need to mount some sensors and program a Megasquirt unit, but that's hardly rocket science. Why mess with jets when you can use a laptop instead?

[quote author=Rocan]oh sonreir... forgot to mention. are you fitting a thinner base gasket? your piston seems a little low in the bore.[/quote]

Hmm... I hadn't noticed before. That pic was taken before I'd assembled for the first time and so maybe there was some give left in the lower gasket. PS I think you mean thicker base gasket.

[quote author=rockcitycafe]what kind of retainers are you running? also, are your rocker faces and cam lobes hardcoated? running higher pressure springs as well as higher lift cam in that top end is likely to destroy the engine again unless the oil issues are thoroughly resolved, hardfacing both cam and rocker arms will help a little[/quote]

The retainers are aluminum and come from R-D Valve Springs. The cam is hardfaced, but the rockers are stock. An oiling mod is almost definitely in my my future (even though I'm still skeptical of the oiling issues on the 360).

As far as solder goes, that was my first trick, but the solder I had wasn't thick enough; it didn't show any marks from the valves and so I switched over to the clay to at least get an idea. I hear wax is a good substance to try, too.

Thanks for the added info!

-Sonny

Nice pistons - what bore did you say they are? And are they available from Arias or are they a special order to your design and mega dollars?

What bikes has small enough throttle bodies to work on that motor? I have sets of R1 T/B and GSXR600K1 and they are rather large.

I think David was asking if you PLAN on using a thin head gasket to compensate for the low piston (negative deck height), rather than asking if you had used a thick base gasket.

As RockCity mentioned, four small pieces of solder are a better idea than clay. I have used both and clay I find hard to measure, but solder is easy to see exactly what is going on.

The pistons are 69mm. I had them specially made by Arias, so they were spendy. I suspect a second set would be cheaper now that they have all the specs, though. The doming should raise compression to about 10:1 and the valve pockets sit an extra .020" deeper than stock. Despite the doming and additional diameter, they each weigh in 11g lighter than stock as well.

As for throttle bodies, I was thinking the CBR600 or possibly the TU250.

No plans for a thinner gasket. That pic was before I had torqued down the head. Take a look at the pics where I have the clay in place. You can see there's a lot less clearance than the previous pic.

Sonreir said:

(even though I'm still skeptical of the oiling issues on the 360).


-Sonny

Click to expand...

Trust me, after 3 heads it is no joke. Take it seriously.

Hey, you're in NYC right? Where did you get the cylinders bored?

Actually, I'm in Oregon. I used a local guy that was suggested by an indy bike mechanic.

I finally got around to picking up a compression tester so I tested the compression on the engine last night. I got 148 in the left and 149 in the right.

Honda specs say a minimum of 155 before you have to rebuild (which I've just got done doing!)

I'm OK with my readings for three reasons though:
1.) I ran the compression test cold when you're supposed to do it on an engine that is up to temp
2.) I couldn't find my teflon tape, so the fittings for the tester were just screwed together without (possibly) being sealed
3.) I realized after the fact that I had the choke on

While I was looking things over, I tested the spark as well. It's a bit weak for my tastes... Mostly yellowy-orange in color and not as fat as I'd like. I suspect a number of causes that may or may not be interrelated (older plugs, replacement of my battery with a capacitor, introduction of Hondaman ignition unit). I'll worry about that once I actually try to start the bike though.

Are the cylinders oiled?

I sprayed some WD-40 in through the spark plug holes prior to the test, but the engine is still "dry".

Don't worry about those CR numbers they are nice and close and will rise slightly when the engine runs and is "wet". Non standard cams drop compression significantly too.

For that weak spark, have you tried inserting a relay into the ignition circuit? It avoids the voltage drops from the two swicthes and miles of old wire.

Thanks for the weigh-in, teazer. I was wondering about the cam affecting my compression reading... I thought it would, but I wasn't sure. I'm pretty sure my dynamic compression at "normal" engine speeds will suffice though (especially because my reading was cold and with the choke on).

As for weak spark, I'm going to leave it as-is for now. I don't want to go changing too much before I've even tried to start the bike. If the time comes that this is a problem to the running of the bike, I will definitely address it.

Just to keep things interesting though, how would I apply a relay circuit to this situation?

Attached is a diagram of my current wiring situation.

For those of you that like to accumulate info: always do a cranking compression test with wide open throttle, crank at least 6 revolutions, you loose 5 lbs. per thousand feet of elevation above sea level.

nice looking motor.


I'm going to use that lemon juice trick.


Do you know what your LSA is on this reground cam? for that matter, do you know what it is on a stock one?


you're gonna get the bike dyno'd, right?



18t on the front sprocket seems like its going to be geared really high. I dropped from 16T to 15T on my 360 and its a night and day difference. Have you done any theoretical top speed calculations on it? well I was bored and did one for you:


Gearing:
Top Speeds at 13000 rpm:
[/color][/size]
(sorry about the font change, i cant figure out how to change it back)
revving to 13500 puts you at 120mph in 6th
revving to 14000 puts you at 124mph in 6th.

with a 17T front sprocket @13000rpms you'd be at 97mph in 5th gear and 109mph in 6th.
@13500rpms, 113mph in 6th
@14000rpms, 117mph in 6th

of course all of these speeds are theoretical, so they would be lower if you included a coefficient of drag into the equation.

Not sure how high youre going to rev that beast, but rpm seems to be the key to speed here. I think you could def get over the 'ton' with a 17T sprocket and get back some of your low speed response.

anyway, great thread.

Hey dp, he has a CJ, they have 5 speeds. I have 17 on mine in more or less stock configuration and it will do fast enough for me, she gets squirrelly about 90. Main reason I did it was to lower RPM's at cruising speeds, which helped considerably for the readability of the bike. That and if I don't rip on the throttle it gets 54 MPG. 8)