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Author Topic: My CB-1  (Read 1546 times)
Dash
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« Reply #15 on: May 09, 2017, 03:01:02 AM »

you'll have to report back how that rear shock "feels".
Fitting the new rear monoshock.



Now it suddenly stands way too tall for the jiffy. Bike stands at a very dangerous angle:




Custom made K&N airfilter. made it bu cutting out the old standard paper thing, then cut out the shape of the new filter. The new K&N filter originally fits the CBR 900 if Im not mistaken.
A knife, some multi purpose sticky goo and some patience and you end up with this:



Works like a charm so far. the bike can now breathe properly.

TO BE CONTINUED

Will do. Friday she gets new tyres among other things so I can ride a bit more enthousiastic in the bends.
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Dash
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« Reply #16 on: May 12, 2017, 12:41:31 PM »

New tyres fitted front & back. Battlax S20 EVOs. Steering bearings replaced. Jiffy extended so the bike doesnt stand at a scary angle anymore.

Wednesday it's back to fiddling with the jets to see if I can get to 60 bhp. Wink
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Dash
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« Reply #17 on: May 31, 2017, 09:57:41 AM »

Results are in. Didn't make it all the way to 60 BHP. But the bike coughs up a very decent 58 BHP and 40 NM of torque. Not bad for such an old bike with very little tuning work done. curretly fitted 104 jets on nr 1 & 4 and 106 on nr. 2 & 3. Runs like a charm and screams all the way to the redline without holding in. Got more usable power in the midrange as well.

Here's the sheet with the graph:



With regards to the weird unknown rear shock: I still dunno where it comes from but it works very well. Bike stands taller, so more ground clearance and the suspension is balanced and actually works now 0_o. In combination with new sticky tires it's become one nasty little corner devil  Shocked

Now all thats holding it back is the size of my nuts when entering a corner. Gonna have to get used to entering corners faster and more agrressive. Grin
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a_morti
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« Reply #18 on: May 31, 2017, 03:47:38 PM »

58hp is very respectable! Is that really just from an exhaust, filter (airbox mods) and jetting?

104 & 106? Aren't stock jets already 105? I seem to remember though, that different companies measure sizes differently. Whose jets did you use?
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Dash
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« Reply #19 on: June 01, 2017, 03:13:11 AM »

58hp is very respectable! Is that really just from an exhaust, filter (airbox mods) and jetting?

104 & 106? Aren't stock jets already 105? I seem to remember though, that different companies measure sizes differently. Whose jets did you use?

As far as I know, yes.

The jets are from Dynojet, I believe.
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a_morti
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« Reply #20 on: June 01, 2017, 04:12:41 AM »

With trimming the snorkels, could you be pinching the effective intake size?

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Dash
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« Reply #21 on: June 01, 2017, 06:22:14 AM »

With trimming the snorkels, could you be pinching the effective intake size?



I doubt it. I didn t change the angle: I only cut off a bit of the downward going tube. So the air doesn t have to take 2 extreme turns but just the 1. I asked the mechanic if removing the snorkels altogether wouldn t improve flow. He told me that CB-1s don't like that. Nor that CB-1s take well to air filter pods in lieu of the airbox.

In short: the flow is quite good standard, as long as the filter isn t stock and the snorkels aren t too long
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ModerateFkr
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« Reply #22 on: June 13, 2017, 02:55:24 PM »

This snorkel/airbox/filter issue is confusing isn't it?

Seems to me we know a few things about how engines breathe, how they can be helped to breathe better, and how the latter improves performance/power. Also, we know that strangling an engine's ability to breathe reduces power, and that this is done to meet power output and emissions regs. Indeed we know this is the case with the CB-1.

So why are we treating it as a special case? More air in efficiently must, at least, surely mean greater potential power out, albeit with some jet juggling and can swapping.

What did Honda do to the CB-1 to make it so sensitive to air intake alterations. This question is all the more pertinent, given the bizarre nature of the snorkel arrangement that draws hot air backwards from BEHIND the engine! That's an odd regime by anyone's standards, even an environment lobby compliant Honda motor corp in the late 1980s. I'm not saying I want the Trump model, just a four cylinder 400cc that hasn't got one of Al Gore's corrupt hands round its throat, and another gripping its balls! Wink)

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a_morti
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« Reply #23 on: June 13, 2017, 03:19:34 PM »

The good news is the 49 state model is more or less the same as the Japanese model. Any restrictions aren't the work of tree huggers in the USA.

Why are the intake and exhaust as they are? The first thing to note is packaging. The cb-1 is a small bike (at least for its era) so you can't have an unlimited size of airbox. CV carbs need smoothed unturbulent air, so that's kinda the point of big airboxes. The snorkels may be to help with that steady flow. I'll readily admit they're also for noise reduction-  the foam baffles attest to that.

Why do the bikes breathe over the engine? I'll answer that with a question. Where are the cb-1's carb heaters? It doesn't need any, but so many period bikes did. You can fill in the blanks.

On the matter of packaging, the silencer is also very small and suits the bike great. That demands compromises to keep noise at an acceptable level, so there is an additional baffle in the mid pipe. Restrictive?  Maybe, but even if so it's worth it for the aesthetic benefit in my opinion.

Anyway... the bike fuels great, it develops sufficient power and sounds amazing. It certainly doesn't feel restricted. The only mods on mine are removal of the intake baffles and that only because the foam was disintegrated.

If you want, you can remove the snorkels, fit an open can, remove the mid pipe baffle and spend dyno time playing about with jets and needles, but for what? 5 more horsepower (be honest, when did you last really really need more) and a load of excess noise? Not for me.

I'm clearly getting old.
« Last Edit: June 13, 2017, 03:24:18 PM by a_morti » Logged

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