Topic: 1977 cb750f2 (915cc)

[FunJimmy]

Aw Man! Don't tell me you changed your identity and moved before we had a chance to ride the Cascade Loop. Chicken. 

[tweakin]

No chance I am missing that ride.  Only thing I am afraid of is the amount of IPA's I will consume in your presence...

Aw Man! Don't tell me you changed your identity and moved before we had a chance to ride the Cascade Loop. Chicken. 

[tweakin]

Minor set back with the bike but all is great know.  The 915 was running excellent with the exception of needed to be tuned but I was not getting 4th or 5th gear.    I must have done something wrong when I shift tumbler / forks back together.  The good news I feel like there is nothing I can't do on these bikes now.

Yanked the engine.


Split the cases and fixed the shifting.


Got everything buttoned back up with out a hitch and it shifts better than any cb I have ever been on, something to be said about taking my time.

I also was able to get close to what I thing is optimal tuning of the RS34's by following Doctor D's guidance, thanks.  132.5 mains, 9DZH03 needles middle clip position, 120 pilots and air screw 1/2 turns out.  Synched the carbs and it has more power, seat of the pants, than I could have ever imagined...  Only a proper dyno tune will tell the entire story onc it is good and broken in.

On another note I picked up my next project, a 1978 cb750f from member Jaguar, Thanks! 


The plan for this bike is to make a nice semi stock daily rider with all my take off bits from this build including the 836 engine and CR29's I have waiting. 

[liPPy]

What was the shifting issue you had and how did you fix it?

New project looks interesting

[tweakin]

My shift drum installation was just a bit off causing the forks to bind.  Pretty easy fix once the cases were split. 

What was the shifting issue you had and how did you fix it?

New project looks interesting

[MCRider]

My shift drum installation was just a bit off causing the forks to bind.  Pretty easy fix once the cases were split. 

What was the shifting issue you had and how did you fix it?

New project looks interesting

Man That's just the kind of thing that worries me. I can't picture your problem. I have shifted mine thru all 5, but that's not conclusive until it's actually running. Or maybe mine will just puke oil out of every crevice, who knows?

Good work, anyway!

[tweakin]

You will be fine, mine shifted thru all gears but it was real rough in 4 and 5.  The second time around it was like butter...

My shift drum installation was just a bit off causing the forks to bind.  Pretty easy fix once the cases were split. 

What was the shifting issue you had and how did you fix it?

New project looks interesting

Man That's just the kind of thing that worries me. I can't picture your problem. I have shifted mine thru all 5, but that's not conclusive until it's actually running. Or maybe mine will just puke oil out of every crevice, who knows?

Good work, anyway!

[lucky]

My shift drum installation was just a bit off causing the forks to bind.  Pretty easy fix once the cases were split. 

What was the shifting issue you had and how did you fix it?

New project looks interesting

Man That's just the kind of thing that worries me. I can't picture your problem. I have shifted mine thru all 5, but that's not conclusive until it's actually running. Or maybe mine will just puke oil out of every crevice, who knows?

Good work, anyway!

When the trans and shift drum is together, you can turn it by hand and tell if it will shift properly.
Matter of fact that is a must do.

[Greggo]

Nominated.

http://forums.sohc4.net/index.php?topic=103091.0

[tweakin]

 

When the trans and shift drum is together, you can turn it by hand and tell if it will shift properly.
Matter of fact that is a must do.

[Doctor_D]

I also was able to get close to what I thing is optimal tuning of the RS34's by following Doctor D's guidance, thanks.  132.5 mains, 9DZH03 needles middle clip position, 120 pilots and air screw 1/2 turns out.  Synched the carbs and it has more power, seat of the pants, than I could have ever imagined...  Only a proper dyno tune will tell the entire story onc it is good and broken in.

Glad to hear that it feels stronger.  Keep an eye on your accelerator pump plunger, they have a habit of not coming all the way back up.

[cheapride]

See splitting the cases isn't that bad just a waist of the weekend.  Did you have your neutral switch in when you first installed the shift drum and forks?  Mine wasn't in until after and it made it a little more difficult.  With your CR's do you use the factory carb boots or do they have new ones?

[tweakin]

Splitting the cases is really easy, just a pain.  Yes, I always have my neutral switch in when putting the drum and forks in.  This time I follows Hondanlmans instructions and all went smooth.

The CRs use the stock boots, luckily mine were in good shape just needed to be softened up a bit with wintergreen.

See splitting the cases isn't that bad just a waist of the weekend.  Did you have your neutral switch in when you first installed the shift drum and forks?  Mine wasn't in until after and it made it a little more difficult.  With your CR's do you use the factory carb boots or do they have new ones?

[MRieck]

I also was able to get close to what I thing is optimal tuning of the RS34's by following Doctor D's guidance, thanks.  132.5 mains, 9DZH03 needles middle clip position, 120 pilots and air screw 1/2 turns out.  Synched the carbs and it has more power, seat of the pants, than I could have ever imagined...  Only a proper dyno tune will tell the entire story onc it is good and broken in.

Glad to hear that it feels stronger.  Keep an eye on your accelerator pump plunger, they have a habit of not coming all the way back up.

I wonder if a stronger diaphragm spring would take care of that Dave? The rubber gaiter may have something to do with that too.

[Doctor_D]

I also was able to get close to what I thing is optimal tuning of the RS34's by following Doctor D's guidance, thanks.  132.5 mains, 9DZH03 needles middle clip position, 120 pilots and air screw 1/2 turns out.  Synched the carbs and it has more power, seat of the pants, than I could have ever imagined...  Only a proper dyno tune will tell the entire story onc it is good and broken in.

Glad to hear that it feels stronger.  Keep an eye on your accelerator pump plunger, they have a habit of not coming all the way back up.

I wonder if a stronger diaphragm spring would take care of that Dave? The rubber gaiter may have something to do with that too.

The plunger actuator (on the throttle shaft) is also on a spring, so too strong a plunger spring may cause other problems.  Maybe some silicone on the plunger shaft, where it passes through the gaiter will help.  If that doesn't work, I'm going to try a slightly heavier spring.

[cheapride]

The CRs use the stock boots, luckily mine were in good shape just needed to be softened up a bit with wintergreen.

How long does the winter green or thor oil tire prep take before the boots are soft?

[Lostboy Steve]

Hey man, whats the inside coated with? You should have someone laminate a picture of that engine split and hang it somewhere on the bike so people can see how beautiful it is inside once together. lol I'm not joking the inside looks nicer than most outsides do!

[tweakin]

I used wintergreen and hot water on the stove and opted not to use xylene.

http://forums.sohc4.net/index.php?topic=62328.50

It has been awhile so I can not remember how long I had them simmer in the mix.  The above thread should be some help.

The CRs use the stock boots, luckily mine were in good shape just needed to be softened up a bit with wintergreen.

How long does the winter green or thor oil tire prep take before the boots are soft?

[tweakin]

Ha Ha, the coating is Glyptal, it is made for coating the inside of engine parts.

Hey man, whats the inside coated with? You should have someone laminate a picture of that engine split and hang it somewhere on the bike so people can see how beautiful it is inside once together. lol I'm not joking the inside looks nicer than most outsides do!

[tweakin]

The sun was finally out today in the PNW so I took the day of and put some miles in on the new engine.  I am still trying to figure out the correct angle to mount my GoPro to my helmet so this is an interesting view.  Sorry if the video make some of you dizzy .  Bike is running great and now have all 5 gears, the initial part of the video is at 2X speed so my bike doesn't really idle at that speed...  Looking forward to some open roads and the engine to be completely broken in so I feel comfortable at the higher rpm's, but you can get an idea.

1977 cb750f / 915

[brandEn]

phukin cool man. How do the clipon/rearsets feel?

[tweakin]

felt great B.  I really like the new riding position.

phukin cool man. How do the clipon/rearsets feel?

[immortal]

Awesome job tweakin!

[Godffery]

Absolutely outstanding work man...!

[messeduptriple]

Wow...I only wish I knew how to tear apart an engine and do a build like that. Great work and awesome bike!!!

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