Topic: CB650 big big big bore kit

[Ibsen]

Actually it's funny you mention the KZ400 carbs. When I first started this project I was going to build a set using the ones from the 400. I had like 5 sets of them laying around. The linkage I would have had to make would have been a nightmare so I eventually went with the set from the honda.

They wouldn't have been my first choice either. To many parts that has to be modified. And another problem is the total lack of spare parts availability. The later Honda carbs are a much better choice.

I still have all of those carbs. Internally they have a better venturi design and would have probably performed better after the tedious set up they would need. Plus they are really heavy as they use that wierd alloy that has a high zinc content, I think its zinc?

Or pot alloy. I'm not sure though.
Also the mounting plate adds a lot weight to them. But you need that plate because of the outlet for the starter system/choke circuit, and because there are no flanges on the carbs them self.  Btw, I know an American 400 owner who needs a set of carbs, so if you are considering selling a rack please PM me.

[speedracer741]

Ok here are the sleeve dimensions as requested: OD 2.723", flange OD 2.950", overall length 4.050".

[paulages]

i sure have got a lot of naysaying--both on here and locally. had one guy locally tell me i was "building a grenade" (he was advertising on craigslist as a "race prep mechanic with a dyno"...contacted him about the dyno, and it turns out he just drops it off at option R in beaverton. hell, maybe we are building grenades.  can't wait to see people eat their words when they're wrong though.

[speedracer741]

i sure have got a lot of naysaying--both on here and locally. had one guy locally tell me i was "building a grenade" (he was advertising on craigslist as a "race prep mechanic with a dyno"...contacted him about the dyno, and it turns out he just drops it off at option R in beaverton. hell, maybe we are building grenades.  can't wait to see people eat their words when they're wrong though.

We may very well be building grenades, but damn cool grenades if you ask me! I think a rev limiter may be a good idea? I think all that really matters is that one has fun doing a project regardless of the outcome. BTW, I will be working on finishing my valve keeper groove grinding machine this weekend so that I may finish the oversize valves. I might just make up more than one set if you are interested in giving them a try? You can be the guinnea pig

[bill440cars]

        Hey Paul & speed racer,

                    Just so you know, I'm fully interested in what you're doing and am taking in the details. I'm wanting to hear about any and all info on what you guys have going. You all are doing what I'd like to do but, don't have the funds to do. Keep up the good work and I'm betting that the pins don't come out of those "Grenades", Hence No Explosion. Keep the info coming.

                                               Take care guys, Bill

 

[speedracer741]

Valve keeper groove grinder finished! This odd looking contraption is something I made to grind keeper grooves in valve stems. It's completion means I can finish the oversize valves for the 741 motor. The grinder motor is just a die grinder. It has a cutoff wheel in it in these pictures as just a test. I have an assortment of arbors and stones for doing different types of grooves. There is a diamond dresser in the tail stock of my lathe for shaping stones for various applications. The main power head is a gear reduction box/motor assembly from a copy machine! The various size sprockets I have that fit on the shaft connect to the valve head via slotted hose and clamps. Normally there is a spring behind it to keep pressure on the valve against the stop during grinding however there is slight angle to the upper pair of roller bearings that causes the valve to "walk" as it turns, also kepping pressure against the stop. I have normally done this type of work in a lathe with a tool post grinder but this machine is centerless (no chuck) so there is zero runout on the valve as it turns. The adjustable stop for the valve stem and stone depth means better consistency as well. The valve I used to test is a CB550 intake. Not a finish grind but just a test to see if there would be chatter....nope, cuts smooth as galss! Now I'm going to make up some good stones, do some practice work and get those big valves done for my engine!

 

[speedracer741]

A few more pics....

[paulages]

man, gotta get together soon and see this contraption. got my head back from mike Mreick, and it looks awesome, so no guinea pig for me unfortunately. i'd be curious to see what you think of it as a head guy. i'm totally open to testing on the 550 engine in my bike though, and have an extra head.  i'm working on the rest, but i'd still love to pick your brain about the 718 (ish) build. get together this weekend  maybe? just got another 750 off of the stand and on the road, and am starting on another---a K6 i bought for $200. changed the plugs and it starts when you so much as look at the starter button... 

[speedracer741]

man, gotta get together soon and see this contraption. got my head back from mike Mreick, and it looks awesome, so no guinea pig for me unfortunately. i'd be curious to see what you think of it as a head guy. i'm totally open to testing on the 550 engine in my bike though, and have an extra head.  i'm working on the rest, but i'd still love to pick your brain about the 718 (ish) build. get together this weekend  maybe? just got another 750 off of the stand and on the road, and am starting on another---a K6 i bought for $200. changed the plugs and it starts when you so much as look at the starter button... 

Sounds like a plan! I will be around all day Sunday. I will give you a call. I do have the blanks to do valves for the 500/550 head. In fact they will probably get done first as I am doing that downdraft port 550 head. The bike for that engine is closer to completion. I have read in the past that larger valves cannot be put in the 550 head however I have not found this to be the case. Intakes are 1.5mm larger and exhausts are 2mm larger. This is the most the stock seats can be machined to handle. Cutting the seats a little deeper in the chamber and unshrouding solves the valve-to-valve interference problem during overlap. This does increase chamber volume but is corrected by proper piston selection. I will post a separate thread for that project as soon as I finish the jigs. I just got the last of the tooling I need in the mail this week!!!!

[paulages]

i'm usually at my shop all day sunday. give me call- the number i gave you is a cell. dan hall is a great guy, but i wish i had found you and the shop you work at before i started my project. seems like it light have been a better fit. in any case, dan's been doing it for years. i have no doubt he'll help me sort through the custom machining without problem, but personal enthusiasm helps for sure. i'm certainly happy with the work Mrieck did.

[speedracer741]

i'm usually at my shop all day sunday. give me call- the number i gave you is a cell. dan hall is a great guy, but i wish i had found you and the shop you work at before i started my project. seems like it light have been a better fit. in any case, dan's been doing it for years. i have no doubt he'll help me sort through the custom machining without problem, but personal enthusiasm helps for sure. i'm certainly happy with the work Mrieck did.

I have heard nothing but good stuff about Dan so I'm sure you are in good hands. I look forward to meeting him as well. Working in the automotive industry during the day I find myself pretty much alone in my interests. A guy I work with races modern superbikes so you can imagine the jokes that fly back and forth between us! Apparently since I'm 29 I should be messing with new stuff. The bikes I put all this work into were obsolete by the time I was old enough to drive.......but they have a style, attitue and mechanical purity that new stuff owes its existance to. Besides, new sport bikes roll down the road all the time with little notice. A CB750 cafe racer rolls down the road and everybodys head turns....nuff said. Well I will see what I can do about making sure one of the prototype downdraft 550 engines finds its way into one of your frames. It would be nice to develop something that could be shared with the world and be reliable but that means lots of test miles and I don't have a whole lot of time these days so you just might be a guinnea pig yet!

[mrbreeze]

i'm usually at my shop all day sunday. give me call- the number i gave you is a cell. dan hall is a great guy, but i wish i had found you and the shop you work at before i started my project. seems like it light have been a better fit. in any case, dan's been doing it for years. i have no doubt he'll help me sort through the custom machining without problem, but personal enthusiasm helps for sure. i'm certainly happy with the work Mrieck did.

I have heard nothing but good stuff about Dan so I'm sure you are in good hands. I look forward to meeting him as well. Working in the automotive industry during the day I find myself pretty much alone in my interests. A guy I work with races modern superbikes so you can imagine the jokes that fly back and forth between us! Apparently since I'm 29 I should be messing with new stuff. The bikes I put all this work into were obsolete by the time I was old enough to drive.......but they have a style, attitue and mechanical purity that new stuff owes its existance to. Besides, new sport bikes roll down the road all the time with little notice. A CB750 cafe racer rolls down the road and everybodys head turns....nuff said. Well I will see what I can do about making sure one of the prototype downdraft 550 engines finds its way into one of your frames. It would be nice to develop something that could be shared with the world and be reliable but that means lots of test miles and I don't have a whole lot of time these days so you just might be a guinnea pig yet!

Sounds like your in good hands there Paul. ....Get yer sh!t running and bring it south this summer!!