Japan Meets Britain

Vince Lupo · Post by **Vince Lupo** » Mon Apr 04, 2011 2:45 am

Well I think we're done for now -- I did about 10 plug chops and almost 180 miles yesterday, and I think it's running about as good as it's going to get, but we're still puzzled by something.....

Final jetting is 250 mains, and the needle in the middle position. No hesitation, no 'nosing over', and plugs look good. Yesterday's temperature was in the mid-50's.

Here's the puzzling thing -- the bike tops out at 92mph (confirmed with a car speedo). 92mph, and the rpms are somewhere in the 7000's (indicated). So why does it redline in gears 1-4, and only manages to get to the mid-7000's in 5th? The current gearing is stock (15/30), and John and I both believe that this bike is capable of 110mph, but it just stops at 92mph. We checked the gas flow and it's totally fine. The K&N filters look good, but I am willing to try it without the filters on another run to see if that makes a difference. Of course, I'm rarely (if ever) going to ride at that speed for my normal riding, but it still is a bit of a mystery as to why we're only coming up with that top speed. On the colder day when I did the testing, I hit 105mph at about 8300rpm, and that was with the 29 rear sprocket and the 530 chain. So I dunno...top speed of a stock CB350/360 was about 102-106mph, so I was expecting at least that, if not a bit more. Right now the bike runs great and is very comfortable with that 30 sprocket under 'normal' conditions, so I'd prefer to not go back to the 32.

I'm going to now put some miles on the bike, do a few more plug chops on my own, and check the K&N filters. I might just wash and oil them this week to see if that makes any difference, but they look okay as they currently are.

Here are a couple of shots of the 'new' side cover on the bike -- this new look is going to take a bit of getting used to, but it sure is a heck of a lot cleaner without that kickstart lever, and I'm glad we went ahead and did the work on it to cover up those holes. Looks much more 'factory' to me than if we just plugged the holes with rubber. The cover still does have a few pinholes, but you really have to stick your face down there to notice them, and even at that they're really not a big deal.

Final adjustments...

Vince Lupo · Post by **Vince Lupo** » Mon Apr 04, 2011 7:43 am

A couple more shots.....

teazer · Post by **teazer** » Mon Apr 04, 2011 11:28 am

Vince, that side cover looks great. Cleans it up nicely.

Those gearing and speed numbers were interesting.

92 at 7,000 would be 110 at 8,300 on the same gearing and would be 113 on 15/29.

Working those numbers the other way, 105 on 15:29 would give 86 at 7000 on 15:30.

Then I tried something else. 8300 at 105 works out to 7500 @92 on 15:30 gearing.

So we can say that the gauges are not clinically accurate.

More to the point, the bike appears to be slightly over-geared and would probably rev higher on a slightly lower gearing (higher numerically).

But that assumes the motor wants to rev and the only way to find out where it peaks is to strap it to a dyno and see the power and torque curves to see what's happening.

The valves may be bouncing/floating. It may need more (or less) ignition advance at the top end with the slightly longer flame path. It's also possible that the fuel slope needs to be tilted.

All the stuff that caused me to lose much of my hair over the years.

In the real world, if the bike generally performs the way you want it to and makes you happy riding it, then it's a success

jensen · Post by **jensen** » Mon Apr 04, 2011 12:24 pm

Hi Vince,

The simple answer is that it hasn't enough power, for the rest I agree with Teaser, especially were he says to get that thing on the dyno.

I made an exel sheet for comparing the four speed to the five speed, remember ?
If you want it to see what happens when changing the secondary drive, it's yours.

When you have the power, but more important, the torque curve, you can "fit" the gears to points in the curve were it runs best. It also determines when you need to shift, from max torque point to another,

I'm also very interested to see what the dyno curves and especially the A/F ratio's show, compared to the 180 miles plug method,

Jensen

teazer · Post by **teazer** » Tue Apr 05, 2011 12:16 am

I'm interested to see where it peaks because it should be faster than 92. Not sure about 110 unless it has a good cam, but I'd hope for as little closer to the ton.

G-Man · Post by **G-Man** » Tue Apr 05, 2011 1:10 am

Vince

Do you still have those baffles in the mufflers? You're trying to put even more gas through them now, compared with the 305 motor..

G

Vince Lupo · Post by **Vince Lupo** » Tue Apr 05, 2011 3:01 am

No, the additional baffles are no longer in the mufflers. There are the factory baffles in the TOGAS, but they're not removable, though they don't really seem to do much 'baffling' -- stand behind the bike when you start it and it kicks you in the face. Actually the engine work made the bike a tad quieter, which is interesting. No longer as ear splitting as it was, though it's still pretty loud - particularly on the overrun. I'll have to do another video to let you hear it!

What I'm going to do is ride it for now and see how it is. I haven't really ridden it much strictly for enjoyment, as I've been primarily been doing 'test' riding with it for the last 400-500 miles. You guys are right though -- I think it's dyno time, but I'd like to wait just a little bit and get a few more miles on the bike before going there. But, maybe what I might do is drop by the dyno place this week and talk with them.

As much as I enjoyed the low end acceleration with the 32 rear sprocket, I didn't like the highway 'buzziness', which is where the bike would be spending much of its time, so for now I'm going to keep the 30 on there.

A couple of years ago, Classic Bike Magazine did a story on Joel Davies and his CB77 350 Read Titan, and I've used that article as a bit of a guide. It had basically the same setup that I have (with the exception of a high-lift cam), and the bike's top speed (as tested in 1969) was 106mph. Now admittedly on the day I did my last tests, it was quite windy outside, so I don't know how much of a role that played in keeping my top speed down, but I'd be hoping that I'd at least come closer to the Read's numbers.