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Discussion Starter #101
decided on a STDThermo Straight Oil Cooler with adapters. plan to replace the oil pan on the 750 with one from a 900F of the same year. the oil cooler kit comes with adapters for the hoses, etc... also decided on a 3/4 fairing and box style café seat from Airtech products. Question for this group; anyone know of a good place to buy the mounting frame for a 3/4 fairing. I need some options as I went with a ducati Pantha 600 style and it has dual headlights. my fabricator can make one, but wanted to see if I can just find one. online, so far, has yielded limited results.
 

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Lastly, do I really need to do something with my oil pump? if so, what's the recommendation? thanks.
I believe you can use the 900F oil pump in the 750 if you can find a good working one. The 750 oil pump will not push enough oil to even support the oil cooler and you run the risk of top end oil starvation.

If you feel like spending money this company in japan offers an upgraded pump: https://japan.webike.net/products/21151771.html
 

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FYI, the airtech glass is thin so you're going to want to have adequate bracing/mounting for the fairing.... as far as mounting, your best bet is to get with a welder/fabricator/machinist and enlist their expertise. You'll pick up some knowledge and have a professional product (for maybe $150-200 i'd say).

Also, japan.webike.net is amazing, and dangerous for your wallet
 

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With a proper suspension and frame bracing, why wouldn't it perform on the track?
It would, the spec is basically what Honda used for Superbikes and 24 hr endurance racing in the 80's 750 was a better staring point with short stroke motor and wide bore spacing allowing 998cc The carbs are a total nightmare without stock air-box though, CR's would be a real nice option. 29's will supply erverything motor needs unless you are building a track only bike (it will still pull at lower rpm, below 6,000 or so)
 

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Neither. Open velocity stacks IIRC.

Way back in the day the late Leon Moss of LEDAR who was a bit of a motor and carb expert, tried to get a CB900 to run with an aftermarket exhaust and he ended up with external tubes to equalize pressure in the carbs. I don't remember all the details but I think it went from rich to lean and back again as the throttle was opened.

I have no idea if that was all one big pressure differential issue or an exhaust resonance pressure wave timing thing, I have no idea.

That does raise a question as to how owners of cars with SU carbs (more or less the same design) get around those same flow/pressure wave issues.
I don't remember if it was you or Kopsicle sent me a lot of information on the Leon Moss modifications? It had internal bypass tubes and converted to 2 jet so they looked stock externally
 

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that's it. that's what i'd like to do, for the most part. i'm not much on the history of the sport, mind you. still learning, so you all sharing this is great! my pic is just a mash up of ideas from various posts. Mostly from a variation of the MotoGuzzi style bike of the same era. YES, a stretch from that to a 80's CB750 F, but wanted to start with some ideas. Here, btw, are some ideas on changes and reinforcements. your thoughts are appreciated.

View attachment 96183 View attachment 96185 View attachment 96187

for those who may recognize these ideas, I want to make sure I reference the project and give credit to the guys who did this. i'm not going to go to the extents they did, but I figure these mods are proven (by now)

https://www.bikeme.tv/index.php/dons-cup-gold-ultimate-honda-cb900f/

several questions still abound, like wider wheels, better forks or just mod what I have, etc.
Those brace points look like stuff Tony Foal recommends and has tested. How many people here have his chassis book?
 

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The 750 oil pump will not push enough oil to even support the oil cooler and you run the risk of top end oil starvation.
I don't understand that.... basically all you are doing is adding length to an oil passageway. Once the line is full of oil, what difference does it make to volume or pressure?
 

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I don't understand that.... basically all you are doing is adding length to an oil passageway. Once the line is full of oil, what difference does it make to volume or pressure?
Length of passageway has an effect on flow rate - when you make passage ways longer you increase pressure needed.

the DOHC bikes are wet sump, not dry sump, so they don't respond to an increase in volume like the dry sump on a SOHC would (which offsets the extra length). The sump doesn't know there is an extra quart in the system, it just knows it has to pump against increased resistance of the added length of pipe.

IIRC too the oil cooler isn't just an extension on an existing passage like most of the oil filter based adapter kits for SOHC 750s, it is a separate loop that runs off the pump and into the sump:

(page 12) http://www.kabalis.com/SuperMagna/CB900-Manual/Honda_1980_thru_82_CB900F_Service_Manual_Chapter_25_81_900F_Addendum.pdf

Os it's not like adding an extension to an existing system so much as it is adding a new second oil circuit. The 750F pump can't keep up with the demands of pumping 2 circuits.
 

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Those brace points look like stuff Tony Foal recommends and has tested. How many people here have his chassis book?
I've got a couple versions of his book, I was keeping up with the updates for a while there.

Or was that a rhetorical question? ;-)
 

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Discussion Starter #110
Any recommendations for a performance high flow oil pump? Right now my plan is to use a 900F oil pump
 

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Length of passageway has an effect on flow rate - when you make passage ways longer you increase pressure needed.

the DOHC bikes are wet sump, not dry sump, so they don't respond to an increase in volume like the dry sump on a SOHC would (which offsets the extra length). The sump doesn't know there is an extra quart in the system, it just knows it has to pump against increased resistance of the added length of pipe.

IIRC too the oil cooler isn't just an extension on an existing passage like most of the oil filter based adapter kits for SOHC 750s, it is a separate loop that runs off the pump and into the sump:

(page 12) http://www.kabalis.com/SuperMagna/CB900-Manual/Honda_1980_thru_82_CB900F_Service_Manual_Chapter_25_81_900F_Addendum.pdf

Os it's not like adding an extension to an existing system so much as it is adding a new second oil circuit. The 750F pump can't keep up with the demands of pumping 2 circuits.
Not that it matters as far as the OP is concerned...... I have to confess that was an incredibly stupid way of expressing what was rattling around in my head, because yes the cooler and lines add resistance....was also thinking the 750 pump was set up in a similar fashion to the 900. However.... although the 900 has a better setup, I still wonder about the real risk of adding a cooler using the 750 pump. They make the coolers for DOHC 750 that connect to the oil filter boss Y/N? 750 F had their issues, but don’t recall any issues with oil supply. 750 Nighthawk yes, but that was an aeration thing.
 

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Discussion Starter #113
well, things are finally starting to progress. Decided to purchase the Kibblewhite Diamond SS valves to go with...well, everything else I've purchased for this project. took one look inside at the valve guides and realized how outmatched I was in dealing with something like this, so thanks to Ryan at Side Street Engines, I now have a professionally prepared cylinder head. behold.
Cylinder Head.jpg
Should be getting the new engine blocks and top crank case back next week. from there, I'll begin working on the frame mods finalizations.
 

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Discussion Starter #115 (Edited)
the frame modifications I have in mind (the Tony Foal influenced mods) are hopefully starting soon. to make it happen, I put the empty engine back into the frame, and kept the wheels on. the plan is to assemble everything, get it running, etc. THEN, when it's ready, make it pretty. unlike the incorrect order of things I followed on the 900 project. also, since I'm installing big bore pistons, I needed a highly skilled machining company to accomplish the necessary borings. CV Tech out of Canada provided these services.

Frame_Mod_Prep.jpg Frame_Mod_Prep_leftside.jpg Frame_Mod_Prep_side.jpg
 

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Discussion Starter #116 (Edited)
I would like to request some advice and/or examples of frame mods to support the racing seat I am planning to use. Here's what it looks like;

cb750_seat_unfinished.jpg

I know it doesn't quite look right today. what i'm asking you all for are examples of what modifications to the seat area of the frame to; a) support this seat in it's proper position; and b) to also have an under-seat battery/electrical box so I can keep the center area open.

also, I have Tarozzi rearsets and mounting plates, but can't find any good, up close examples of how they're installed. anyone have any pictures for these i'd also like to hear from you.

as always, any input you all have is appreciated.
 

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Seat looks way too tall, can you section it to get a better profile? Easiest thing to do would be sit on it and get someone to take a profile picture, should give you a better idea of how it looks and feels. As for Tarozzi's, there are tons of pictures of them fitted, including close up. If I remember right, the web site showsfittings on a stand, makes it easier to see where things go. They are very adjustable, setting up may take some time
 

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Discussion Starter #118
thinking I need to carve out the area around the top of the shocks so it slides down and sits flush to the frame. hard to see as the original framing is still there and throws this off. i think if i can lower the seat to a flush position and put my Ohlins on, which are 1" longer than the stock suspension, the optics will be better. I'll check the web site for Tarozzi again, but their examples for this kind of bike is a bit limited.
 

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Seat looks way too tall, can you section it to get a better profile? ....
Agree! Please follow those body lines from the tank.... just waking up to a busy ass day, but needed to quickly comp something to give you another perspective....

By far the shittiest photoshop job, but if 1min of my time helps you, then it helps all of us. Keep us posted.

option_seat.jpg
 

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When you talk about lines and stuff you totally lose me, I'm a function over form kinda rider :| and for me either of those saddles would force me too far forward on the bike, which would make it less functional. Motorcycles that have a seat/tail like that would also have a longer fuel tank.
or you are way tiny then me and ride weird.
 
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