Starting Work on CB750-1001250

[BenelliSEI]

As noted in my “Introduction”,  I recently went on a bit of a road trip to buy an interesting 1975 Amen/CB750 “Chopper”, late in January. Not my typical bike, I’m currently working on a ‘75 Rickman Honda CR and most recent project was an early, diecast K0. Also in my shop is my regular ride, a very clean K1, sitting with a K3 my son rides, my wife’s “flake orange” K4, and a K6. My son and I also have two more fully restored K7 and K8, that have been parked for the past few years. The chopper was reasonably priced and the original owner sweetened the deal with a “parts bike” that he had picked up +35 years ago. When I got there, I spotted the horn on the “wrong side” of the parts bike....... I loaded up and brought every thing home. I’ll attach a few pictures here.

[BenelliSEI]

I’ve spent a few days, slowly pulling the motorcycle apart. Interestingly, nothing seized, stripped or destroyed. Today I removed the swing arm and the bolt undid easily, and just slid out! Clearly this bike has never been left outdoors. Basically have it down to the bare frame, oil tank still attached. Carbs, handle bars and both switches were missing, but essentially complete. The horrific luggage rack and crash bars have been binned. I have a set of carbs (non 28) that I’m cleaning up. The engine is free, turns over easily on the kicker, and I can find all the gears. I have the bores soaking in oil that I fed in through plug holes and intake runners. The exhaust is very original and despite a few marks and small holes, is saveable. Thinking I might built a basic wire loom (power a solenoid with a remote start button and coil feed) to spin it up? Check for noises and decent oil pressure. If that all works, do a “3,00 mile tune up”, install the fresh set of carbs, new plugs and fire it up?

[BenelliSEI]

Earlier one of the forum members here asked about case marks on the engine. Today I found a couple, just to the right of the drainage slot in the top case. They look like my sketch here. What do they mean?

[BenelliSEI]

A few pictures of my K0, to offset the Chopper photo!

[BenelliSEI]

Yesterday I hung a solenoid, start button and a few cables on the frame. Been “oiling” the bores and turning it over on the kick lever, all week. Top end is oiled, valve clearances checked...... installed an oil pressure gauge. This bike has been parked for +35 years.

Spun it up and within seconds, 70-75 psi oil pressure on the starter (plugs out). Next will drain the oil and have a look at the filter element. Currently rebuilding a set of carbs. Tempted to blow the cobwebs out of the original pipes, before I pull the motor. I’m thinking this one will only get a top end checkover! Quick hone, new rings and cleanup the head. 17,600 original miles.

[kp]

That's a good outcome. My #28 had been sitting for many many years and was stuck solid when I took delivery. After 6 months with aero kroil in the cylinders and ratchet strap on the rear wheel it wouldn't move, so I decided to pull the engine. I pushed it of the centre stand forgetting I still had it in third gear. As it came down the rear wheel bit the tarmac and would you believe it the engine freed. I pulled the engine to check the bores but couldn't recover them due to the long term seizure. Ended up with .25 over, head renovated and a complete change of gaskets and seals. While the engine was out I did a thorough clean and fix up of anything needing attention. Due to the very poor condition of the paint, a full repaint with crack repairs  was the only major cosmetic work done. I also re-anodised the switchgear, re-clearcoated the alloy and machine polished the chrome.Once it was all reassembled it started first go, the only issues being an oil leak which turned out being the neutral switch and 2 floats needing replacement. Here are before and after photos.
Good luck

[BenelliSEI]

More fun today, installed a set of carbs I just freshened up, checked valve clearances, set points gap, static timing and opened the remote fuel tank valve. #2 carb had a tiny split, right up one side of the over flow tube (all inside the bowl). Heard of this, but never seen one. Frozen condensation? Soldered it up.

I’d installed an old truck solenoid and starter button, with a power feed to the coils. Pushed the button and she started almost instantly. No smoke, rattles or issues. 70-75 psi oil pressure  (screwed a gauge in the main cross feed gallery).  Primary and Cam chains absolutely quiet. Smooth idle, clicks through all the gears effortlessly.  What a BONUS day. This engine has a small head gasket leak, “top end” work only

[4pots1969]

Hi,
When it happens like that, it's a smile and a good motivation for the future, happy for you!
I think with a lot of skill you will be able to straighten the bent cylinder block fins ... I had a cylinder head fin fully seated on top of the one below and managed to reassemble it fully and also to straighten a lot of twist fins on the cylinders ...
I take small oak wedges and I strike with a not too heavy hammer but the cylinder or the cylinder head must be free to move when one strikes to absorb the shocks of the hammer ... But it is important not that there is a crack start ... And do not count the time spent!

[BenelliSEI]

Thanks for the encouragement! Dumped the oil and filter after a good warm up. Plan to run some clean oil through before pulling it out. The top end will come off and I will work on that damage when all the parts are separate and clean. I’ll take some pictures today.

[BenelliSEI]

Ran it on Fresh oil/filter. Sync’d the carbs and really smooth and quiet. Repaired float bowl cured the drip. The two hole rear fender arrived. Beautiful, original, so no more missing parts. Need to strip it all down, and start some serious renovations. 

[Wayne]

Nice to see you making headway John. Did I see on FB you’re looking for rims? Yours pooched? If the rear is a rolled rim I think they’re a tough find.

[BenelliSEI]

Thanks! Not me, rims are fine. Including the correct rear. These parts will be replated.

[BenelliSEI]

More progress today.

[Wayne]

Good stuff John. I’ll be watching as the project progresses.

[BenelliSEI]

Repaired small holes in the rear foot bracket tubes, where a P.O. had welded stays for the luggage rack. Found a local “Hot Rodder”with a large media blast cabinet. He also has a small spray both and excellent paint skills..... going to head over there and see if we can clean up parts and do some priming and black paint on the frame, swing arm etc.