CB750 scrambler project
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Together they look like this.
Brat style
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Frame is now powdered
New tapered headset bearings installed.
Front end half on
New top bushes for the rear shocks to make it compatible.
Here's a little mock up.Just waiting for my new bike lift to come.
I've got some pod filters on order + crank case vent filters.
Rejetted carbs using an online calculator (I will fine tune but as a starting point for the intake and exhaust mods)I have a slightly nicer/longer seat now which will suit my stealth appearance.
It's very hard to visualize in your head but I think it's looking more or less like how I hoped
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After a bit of haggling I got an engine from a 12k mile bike (running) with warranty. I believe that is genuine, I will remove sump and cam cover to inspect+ comp test. And flush the lubrication system.
However the seller advertised it as a CB 750 nighthawk 1992 to 2003. It looks identical apart from what I couldn't see in the pictures.... It has No clutch arm!. Meaning it needs a hydraulic slave cylinder.
Also the electrics are not compatible with my loom, the cbx750 engine has loads more wires for shift lights, selector drum position etc.
I've now got to get the pulse generator sorted, source the main generator+ cover, starter motor+ cover.
The CBX has larger valves, maybe just exhaust?
Both engines have pros and cons.Right enough spending for a bit
luckily selling some old DT parts has really helped.
A bit of elbow grease and this engine really came up .... I haven't even painted it
Thinking about mounting the lights to this and using the slots for height adjustment.
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@Louis-DT-WR loving the build so far. I fell in love with honda back in the late 90's after owning an nc30 for a couple of years. I must say for a "probably going to take a long time" project, (your words) lol. You have sure progressed quickly enough. At this rate you'll be riding it within the next week or two.
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@markus-w thank you, I still need so many parts.
I have no experience with these bikes so i don't know how anything goes.
I need all the brake/ clutch hoses, front will have to be custom.
Levers, pedals, footrests, controls. Cables.
The biggest headache is the electrics.I can't understand why it's a push pull cable on the diagrams when the CV carbs are sprung loads on the butterfly valves. Doesn't make sense.
This engine is all new to me, I can't get any information about what year and model bike it is. Engine code is RC17E.
I'm not entirely sure if this is a breather pipe or a return pipe ..,.
Can see it on diagrams, it looks like it bridges the two sides of the cylinder assembly.
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Wheels on.
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@Louis-DT-WR I think it is spring loaded as well with the push pull throttle cable or how else would the throttle shut off when you let it go? Or have I miss interpreted you?
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@markus-w it only needs a single pull cable same as the DT but the diagram shows 2 cables.
This pipe in the front of the engine must be a breather I can't see what else is would do.
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@Louis-DT-WR you're probably right on it only needing one cable but U.S DOT requires two by law incase the spring fails or throttle slide sticks. Contrary to their name they don't actually push, when you shut off throttle the push cable actually pulls the throttle closed. As for the dtr having single cable maybe they weren't sold in U S.A or maybe that law comes in for bikes of a certain size/power. My 1989 nc30 had two.
And yes it is a breather pipe, they sometimes are routed back into the carb manifold so any nasty emissions are burnt off. Hope this helps. -
@markus-w great thanks but I have a dt200wr which was sold in the US and that wasn't push-pull.
The carbs to have slots for two cables day + choke cable.the CB 750 doesn't seem to have that breather pipe, but on this cbx750 it does.
Brains hurting from all the learning on this build haha.
I'm happy the rolling chassis is done.
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@Louis-DT-WR my thirst for knowledge has got the better of me I've just done a bit of googling and apparently it's only four strokes have 2 cables because the extra vacuum created by a 4 stroke can cause the throttle slide to flutter and jam against the side of the body. That seems to me the most logical explanation so far.
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@markus-w possible. The other thing with this engine is why does it have 2 oil fillers caps
️ 1 says (don't open) but that's the sprocket side.
In some pictures I see that's where the dipstick is on some bikes. My dipsticks on the clutch cover side like most bikes.Haynes don't do a cbx750 manual.
Just going to persist working through all the small bits. -
So the carbs were very similar but not correct.
So I started again
parts are taking so long to come from overseas
All new float bowl gaskets, diaphragms, o-rings and rejetted.
Powder coated partsStainless steel Allen cap bolts
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Finally my bar clamps came, 3 weeks.
I've got the controls, grip, master cylinders on. Front brake operational.
Choke and throttle cables.
Front headlight on the number board (not finished yet) more to add to it.Pro taper contour bars.
Rear fender (when pulled out, it's a shovel! (Entrenching tool))
Slowly making progress.
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@Louis-DT-WR i like the shovel rear fender adds character
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Been driving me crazy how the seller of the engine said it was from a cb750 but appears to be a cbx750 engine (much older + hydraulic clutch) rc17/17E
But the engine apparently had only done 12k
Also looks very new for something that would be 40 years old nearly.After a lot of research the Japanese did a later 2007 LTD with the Rc17E engine when looking at the part numbers for the upper crankcase on this models parts diagram it confirms this.
This is a super rare models engine, + hydraulic clutch optional extra. On an import!But it will work perfectly for me, just ordered the correct pulse generator.
Writing this down for future reference because I'll forget.
