CB350 wanting as much power as my wallet can afford.

Nicely written article Sonrier. I advise all, vets and noobs, read it.

With that being said. There are some key points made in this article that need to be acknowledged. Here are some detailed tech tips to expand on some of the prior points to help fine tune your Cafe's power and handling:
"A cafe motor is a giant air pump" - Meaning the easier you allow this motor to breathe the bigger the power gain, HP = (T x RPM) / 5252, and improved response will be. The importance to this is the Power to weight ratio, (HP/Mass), being a key characteristic more so in a motorcycle than a car.
Let me explain:
1) By improving the intake and exhaust, and proper jetting, you can gain 2-4 HP. which is significant for a bike that only has 35-40HP stock
2) Running lighter tires and wheels you can reduce Centrifugal drag on the motor which will gain approx 1 HP. Run proper tire sizes and air pressure.
3) Running the proper chain tension you can put the gained power of the first step more effectively to the ground by reducing any lost inertial energy through too much slack.
4) Polishing or simply cleaning the touching surfaces of your Brake backing plate (s) and wheels you can again reduce lost inertial energy (Less Drag) - http://racetech.com/html_files/TechTipFloatingBrake.html
5) To improve your braking have your front drum and pads arched - http://www.racetech.com/page/title/Brake Arcing
6) Lube or replace your throttle cables to increase response. Clean the throttle tube and housing but do not lube them. This attracts dirt and can create an issue.
7) Lube or replace your clutch cable and lever to increase comfort and efficiency.
8) Upgrade your suspension to improve handling, braking and comfort. This is as effective as the first step in gaining HP and being able to put it to the ground.

These few tech tips cover the basics in making any running cafe a SAFE and reliable scoot, and will gain a little more power while you're at it. View the two links I posted to read the significance of those improvements in depth.

Best of Luck, Merry Christmas, and keep it on two wheels.
 
xb33bsa...Step 4 may not apply to you, because your rear wheel bearings, bushings, axle and backing plate were kept in pristine condition. But to a majority of others on here who didn't buy the barn find gem that you did, this is a valid point... By adding drag to the rotation of the rear wheel you will decrease your HP to the ground and negatively effect the travel in your swing arm. Thus inhibiting your speed and handling ability. And going back to the Power to weight ratio equation posted prior this can be significant. Click on that link I posted. It might shed some light...FYI - It was also written by the very Knowledgeable Paul Thede.

Next time you take your rear wheel off take a look at the gunk in the grooves between your rear wheel and the brake. Then place it back in the wheel and rotate it around so you can hear the drag the backing plate creates when touching the wheel. When cleaned properly this backing plate and wheel should be silent and smooth when assembled.
 
that shit dont rub no need to polish it he is talking about floating brakes,and dirt bikes no need to confuse people on here with shit that does not apply
i know who paul thede is, he is race tech, and was a sponsor of mine back in the day
if the backing plate rubs something is bent
yes it is possible to have enough crud in there esp on a dirtbike
 
I'd subtract 10 hp from those numbers for a stock engine. Wouldn't want him to still see lower numbers after throwing a bunch of money at it...

MXSeatPro.com said:
1) By improving the intake and exhaust, and proper jetting, you can gain 2-4 HP. which is significant for a bike that only has 35-40HP stock
 
Once you get it running really good in it's current form, a relatively inexpensive thing is a little shot of nitrous oxide. You can go from mild to wild with the push of a button. You can set it up to easily increase power by a significant amount. Drag bike guys use it all the time. One of my good friends is inching ever closer to 200mph in the quarter mile on a fully modified drag bike using N2O (nitrous).

Of course, there are risks. Improperly set up, it can do a lot of damage in a hurry. I used to hurt stuff in my race car all the time.
But a little street system can give you a big boost on demand without affecting everyday ride-ability. I would absolutely NOT do this if the thing isn't optimized to begin with. It's just asking for trouble.

The golden rule is if you are afraid of breaking it, then don't do it.
 
A decent N2O setup is difficult for an amateur to pull off on a carbbed setup. Dry shot is asking for trouble and wet shot needs a lot of extra equipment to do properly.

If you're going to mod the engine, compression and bore are "easy" options to begin with. They require a little machining, but there's a lot less risk involved when compared to other possible modifications.
 
Words of wisdom Sonreir.

A wet system requires not only "the Bottle", solenoids, injectors, wiring, switches and plumbing, it would also require an auxiliary fuel pump and fuel pressure regulator and a good bit of knowledge.
The main point is that a well set up system can add a bunch of power without compromising "ride-ability" and usable power band that would come with engine mods.

For example, a healthy CR increase, while adding low end punch, will most likely make more engine heat and in some areas getting past a certain point on the CR will cause problems because good enough fuel is not available. Detonation will eat an engine alive.

Bigger cams would move the usable power to a higher rpm and most likely sacrifice low end power. Same with bigger carbs and exhaust.

Head work is by far the biggest bang for the buck, and that is really where the biggest power increases would come from. You can put a bitchin' set of heads on an otherwise turd motor and turn it into a screamer. On the opposite side, a set of stock heads on a bitchin' motor will most likely not deliver much more power than a stock motor by restricting the ability of the motor to live up to it's potential.

It all needs to be balanced with everything else. With engine mods, most likely, one change demands other changes and adds to the cost. Add to that, each modification that increases power will require a corresponding increase in fuel flow. Example - Higher flowing heads will need more fuel to go along with the increase in moving air. More aggressive cams, same thing. Higher flowing exhaust, same thing.

Based on that, a nice little nitrous system can provide sizable power increases at a lower cost.

Whichever way one decides to go, the golden rule still applies. If you can't afford to break it, then don't race it.
 
And I think that's the crux of the point. Don't make changes unless you understand the ramifications. It's perfectly acceptable to swap out to a hot cam and trade some low end grunt for top end power if that meets the goals of your build.

By changing the design of your engine, you're effectively saying to the world, "I think I can do a better job than the engineer that worked at the factory".
 
Step one. Put all CB parts in box.
Step two. Wrap box in chains.
Step three. Throw box in river.
Step four. Install this:

Step five. Turn throttle.
Step six. Annihilate friends.
Step seven. Pick woman of your choosing.
Step eight. You can figure the rest out.
 
Not for nothing, but these engines on the CB350 are already highly tuned. 36Hp (Crank) out of about 24CID. Twin carbs tuned exhaust, large ports (look at the intake ports on the engine, then look at a car with much larger displacement....

The only way to get more HP out of a stock engine is to deviate from stock a whole lot. (A whole lot of $$ too).

I bet you would be surprised at the performance of a STOCK, well tuned CB350.

Most people getting any significant HP out of these motors have spent more than what a clean running stock bike is worth.....

You could spend $5000 on the motor, and still get spanked by a dead stock 600cc anything....

A stock machine gets in the neighborhood of 24HP to the rear wheel. For a few grand, you can get 27, 28 HP, or spend more and get low 30's..... Still not a whole lot....

I suggest getting is tuned well in the stock mode. If the bores are worn out, go up 2 sizes, but don't do it if it doesn't need it.

If the carbs work, keep em.... Look at the posts asking how to jet the Mikuni's. An EXPERIENCED mechanic with carbs can tune them, but it is really difficult for the back yard mechanic type to tune carbs, keihin or mikuni....

With stock compression, a good tune up, clean and adjusted carbs, those bikes were plenty fast for what they were. It is far easier to get them running well stock, then it is to get them running well modified, especially if you didn't know how it ran when you got it. Some people seem to think the mods made the bike perform well, but they don't have the the actual expereince of a stock bike running well to compare.

My 350 could outrun Triumph Single Carb 500's in the early 70's. (only on speed though, the damn Triumph handled so much better....Took turns like it was on rails).

Make it really good stock, then decide on what you might change, and you will have a baseline to compare too.

In 1971, these bikes were fast....(BTW, 250 cc 2 strokes would still eat them for dinner)...
 
VonYinzer said:
Step one. Put all CB parts in box.
Step two. Wrap box in chains.
Step three. Throw box in river.
Step four. Install this:

Step five. Turn throttle.
Step six. Annihilate friends.
Step seven. Pick woman of your choosing.
Step eight. You can figure the rest out.

Is this a 1st model year Kaw. 500 ??
 
Stock cam is OK and shitload cheaper than going Megacycle, etc
Max overbore as it sound like you have to bore it
Do absolute minimum to clean up intake port, it's already too big.
Exhaust ports can stand some work though as they are a little small
With rear sets and clip-on's, raise gearing slightly and it will easily DTT ;D
The biggest improvement you can make is fit better ignition, stock points cam is designed to give 'points bounce' around 10,000rpm, it's possible to use a sharpening stone on points cam to reduce the angle slightly so bounce doesn't occur until later but it is a PITA to get right
Myd, stock motor can easily get 33bhp at wheel with very little cash outlay, but
1. you have to know what your doing
2. it takes a bunch of time
3. I'll need to 'fix' stock carbs (saves at least $200 on Mikuni's)
It will still get spanked by any 600 from about 1985 on but can scare a bunch of them if you find twisty enough road ;)
 
If you want a super fast CB350, visit your racetrack when they have a vintage event going on. There are TONS of super fast CB350's out there.

Or, give Todd Henning a call and have him build you a screamer!!!

http://www.thrhonda.com/THR/CB350_K4.html
 
teddpage said:
If you want a super fast CB350, visit your racetrack when they have a vintage event going on. There are TONS of super fast CB350's out there.

Or, give Todd Henning a call and have him build you a screamer!!!

http://www.thrhonda.com/THR/CB350_K4.html

You can also watch the similarly displaced 2 strokes do laps around these super fast CB's :)
 
Go big bore. Should be able to get 435-450cc with liners with reliability. A megacycle cam one step down from full race, mild port work and 34mm Mikuni's will get you about 45hp at the back wheel easily. The bike will be a bullit!
 
Kemp said:
Go big bore. Should be able to get 435-450cc with liners with reliability. A megacycle cam one step down from full race, mild port work and 34mm Mikuni's will get you about 45hp at the back wheel easily. The bike will be a bullit!

What Kemp says is gospel. He knows, really knows, more about motorbikes than just about anyone. Fact.
 
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