Newbie need Cb 360 engine recipe

G

Goingforsound

CB360 & CL360
Hi guys,


I've been reading the forum for a while now and just registered yesterday.


I've been looking and searching around for a ''engine recipe''. I know that if I keep reading I'll ben able to gather the info slowly but I am in a hurry to get started in the project, as every newbie...

My CB360 76' will need the following:
Piston, gasket set, carbs, points, coil and wire, velocity stack, timing chain and tensionner

I wanted to get a tried and true list of parts to match together. Everyone seems to have a different setup.
The goal is just to upgrade a little bit the original engine while I am doing the rebuild.

Here are the questions:

1. Can I buy one of the ''NOS big bore kit'' I see on ebay? They are really cheap, I am worried about their lifetime?
2. What type of carb I can instal with velocity stacks, that wont be hard to tune, while giving me good improvement on power. Am I better off with a simple rebuilt kit and the stock carbs if I dont want to spend much time tuning it?
3. And for the ignition, is there a way to improve the stock system without swapping electronics?

I want to spend wisely, but I want the bike out of the garage soon, that's why I'm asking people that know their stuff ;)

Thanks,
JC
 
If youre going to do anything other than stock, youre going to have to tune, bottom line. Theres no quick and easy set up because every engine, even if its using the same parts, is going to run slightly differently.


If you want the bike on the road as soon as possible, id skip the big bore kit, skip the velocity stacks, and look into one of the transistorized ignitions (hondaman on SOHC forums makes and sells them for a really decent price), but you can skip that too if your ignition system is in good shape. Just grab one of the aftermarket gasket sets from ebay for like 30 bucks and replace them as you go. Get a carb rebuild kit (2 of them) and rebuild the stock carbs, get new air filters and plugs, and you should be good to go. This is all assuming the bike runs decently well now. If you have problems that require massive engine work, it might be a good idea to look into big bore kits and what not, since you'll be paying for machining anyway.


Do you have any experience building engines? Its probably going to take longer than you think... If you start now id say best case scenario you'll get the bike on the road in a month or 2 months. But generally the way it goes is if you start building at the beginning of one season, you wont be on the road until mid next season :P
 
Thanks for the answer.


Yes, I got experience in rebuilding engines. The bike need to run for next year only, but I dont want to extend the projet for two seasons!


I really need at least an oversize, compression is really bad.


I dont mind a bit of tuning, I just dont want to have a race only carb setup that will be very sensitive or impossible to run on the street


I'll write a bit more tonight, I'm at work now.


Thanks a lot.


JC
 
Well, if youre gonna go oversize, just grab a kit from a reputable seller, either on ebay or through one of the aftermarket parts websites. Check the feedback and google around for the kit name and see if anyones had any problems with it before you buy. I wouldnt buy bottom of the barrel stuff for something as important as pistons, but thats just me.


As for carbs, the best bet for reliability and consistency and low speed power is gonna be the stock set up. You can get pods and velo stacks (i run pods on one of my bikes) but theyre kind of a pain in the ass, both from a tuning perspective and a consistency perspective (a cross wind can screw with your fuel air ratio with pods and velo stacks, for example). They still make jets for your stock carbs, so just buy the next 5 sizes up and try them out till you find what you need. Dont fall into the trap of trying to drill out jets or modify them or anything like that. There are enough sizes you dont need to do that, and its not worth the 20 bucks you'll save.


If you want to go aftermarket on the carbs though, the mikuni VM's are decent, but you will need new throttle cables and maybe a new intake to get them to line up (not entirely sure for the 360). Youd probably want the VM28s for that bike, you could make due with the VM30s but theyre probably going to give you a lot of tuning problems.


I guess the bottom line is the farther you go from stock, the more trouble youre going to have finding a good tune for the bike. Its really a trade off. You can try and get every bit of power out of the engine, but the return on investment (both money and time) starts to drop off real quick. If you want a reliable ride that you dont have to tweak every other day, and just a bike you can go out and cruise on and have fun, stick as close to stock as you possibly can. I like tuning my bikes and wrenching on them but i always have one thats almost bone stock, just so if something blows up im not stuck without a ride.
 
1.) If its the same "big bore kit" I saw on eBay, avoid it like the plague. The "kit" is actually just a set of +3mm pistons and rings. The stock sleeves aren't going to like that much taken out of them. Upper limit for stock sleeves is about +2mm over. A guy I know does run +3mm, but he rebuilds his engine two or three times a year.

2.) You stock carbs will work with a stack, but not too well with a pod. The move to a stack will require a rejet.

3.) I'll second the Hondaman suggestion. A transistorized assist will get you a stronger spark, especially at low and high RPM. You can also make the switch to a coil from an XS (www.mikesxs.com), but it will require a bit of fab work to mount up to the bike. I've seen some evidence to support the idea that iridium plugs can get you a bit of extra oomph.

Other modifications to consider would be some aftermarket pipes (buy something proven on the dyno). There's also the option of raising compression by decking the head, but that will also require retiming the cam. And last, but not least, a turbo system. ;D
 
FYI, here's the list of mods my engine is in the process of getting:

*MegaCycle cam to increase duration from 221° to 251° and lift from .341" to .381" - $308
*Custom pistons and rings at +2mm over (raised compression from 9.3:1 to 10:1 and milled valve pockets for an extra .020" clearance) - $407
*Aftermarket valve springs to deal with the increased lift - $181
*Custom copper head gasket to compensate for increased bore and compression - $28
*Machining (boring the cylinders and lapping the head and jug) - quoted around $180
*Velocity stacks - TBD (I'm still shopping)
*Assortment of new jets for the carbs so I can tune it in- $22
*Gasket kit - $38
*Hondaman Ignition - $75

I'm up to almost $1300 and still counting. Extra ponies don't come cheap and don't come without effort. When it comes to adding horse power, pick two: Cheap, Effective, Safe
 
You can also use GS850 pistons. They are lighter and the skirt is shorter. wrist pin is the same.
I'm told that you can machine the case and a cb400 twin and get longer stroke. You also get piston rods that come off the crank so you can change bearings. I have no first hand knowledge of this. But I've seen a write up i can't find now. I mentioned this to my bike mechanic and he says he has heard the same thing, and thinks he knows what to do. I don't have that kind of cheddar though.
 
and don't forget the weak cam bearings and oiling in the top end, would be great to make more power, would suck when the cam grinds itself down through the head... it would probably be easier to get a 350 if you want a small displacement twin that will make power
 
What year is it and how many miles does the bike have on it? Is the engine apart now? How did you check the compression? Plugs out, throttle and choke wide open and either kick it over or spin it with the starter until the pressure stops rising. Cold should be 165 psi hot should be 170+. Some times a hone and re-ring will fix that issue. MEASURE everything you can get your hands on that is in the manual and see how far out everything is. Buy a feeler gauge and a digital micrometer if you don't already have one. You need the gauge to set the valve clearance anyway.

Do the valves leak? Pull the carbs and the pipes off enough you can get your ear down by the ports and spin the engine over slowly. There should be no HISSSING only a POP or an inhale sounding noise when the ports OPEN. IF the valves leak that can be an easy a fix as a regrind and lapp to ensure seal. Unless they are bent.

The top end oiling issue can be fixed for the most part don't let that scare you. ALL these bikes have issues with either oiling or cam chain tensioners or god knows what because the former owners didn't take the time to do proper maintenance. 360's had two recalls done on them, one for the cam tensioner, one for the rocker arm pins and valve cover bolts. The engine number should have to DOTS above and below the - in the number.

Do some measuring first, then decide what needs to be done. If you have to have the jugs machined expect that to at least take 2 weeks to 2 months depending on the person doing it.
 
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