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Fixing up a friend's 1992 CB750

Got the forks sorted; made a oil seal installation tool out of 1 1/2" PVC pipe on the lathe, used a pair of bar clamps to press in the seals. Only had to replace one slider, the others in good shape. I chickened out and filled the tubes upside-down, cut down a funnel for a tight fit over the fork bottom tube, then poured in the fork oil. With the end and drain bolts tight then flipped each fork right-side up for the seals. Only forgot one of the spring clips, but just for a couple minutes ;)

Cleaned up the speedo gearbox, came out great- there was a bit of grease still in there beneath all the dirt- on a roll! Checked his front wheel bearings, one barely turns the other is frozen far as I can see using fingers... of course... so off to buy him some new front bearings & seals lol
 
If the bearings are in with the same retaining ring my '79 has, you will see two dimples in the groove formed by the mating threads. Drill the dimple out ~1/16" (past the thread distortion). I made a removal tool out of a long piece of 3/8" scrap aluminum with two holes drilled the appropriate distance apart to match the holes in the retaining ring. I used drill bits with the shanks through the holes to insert into the ring and unscrew it. Used the same tool on the rear bearing retaining ring with an extra hole drilled for the bigger spacing.
 
Front wheel bearings replaced, they press in the usual way- rust coating the inside of the wheel from the water leaking in sheesh. So washed it out with alcohol, cleaned everything up and got the front end back together. I ran the engine a bit, the leak I thought was oil turned out to be gas dribbling out of the right-most carb, so I have a set of new seals & rings coming and will pull the bank back out this weekend. From chatting with my friend the engine sounds likeit runs way lean, unstable idle & liable to bog until warm which I noticed too- so I'll look into fuel/air adjustment but am not going to do a jet kit for him or start drilling the idle jets.

The exhaust leaks seem primarily from the joints where the 4 downtubes enter the manifold unit under the engine, so I'll try to seal them as best I can- I don't think my friend is likely to pony up for a new exhaust and in any case I'm really skeptical about removing the exhaust- those studs look scary.
 
While the carbs were on the bench I looked into the pilot screws. 2 of them were at the OEM 2 3/4 adjustment, the other two were way lean because the pilot head pointers were set to the same position but getting the oddballs to the OEM adjustment meant they would need to unscrewed almost half a turn past the others. Given the bike has always been chronically lean I put all four pilot screws at 3 turns out.

My friend came over for some bike therapy- we got the carbs back in,and the front brakes bled- happily the master cylinder is working. Engine started reasonably well and the idle was <<way>> better, though at least one cylinder is not firing well. He test rode the bike- even after the limited exercise the engine had started improving a bit. I did a quick field adjust of his idle stop but it needs more- and I'm going to do a carb sync given the dramatic improvement in engine performance. He did a couple high rpm drivebys- engine revved well, sounded good at speed. We'll see how it settles out.

There is no oil leak, I took the opportunity to smell his exhaust- gas odor there presumably from the unhappy cylinder.(s) When he rode up, there was no smoke which did resume while he as at idle standing there. I put in some Wynns powershot, we'll see if it has much effect. He needs new tires, but thats his problem lol- new front bearings and overhauled front brake did great- very pleased with them.

We parked the bike alongside the garage because I want to look into my R6 front forks- I'm a hypchondriac sometimes and want to check over the forks a bit. While we were getting his bike into place a storm came up, darned if he didn't say just leave it out in the rain "won't hurt it"- NO NO NO, its hurting ME lol so I put the cover on. I'm going to harrass him a bunch about that lol

So anyway, this is looking like a successful job getting him back on the road.
 
Just an update for posterity in case it might be helpful. My friend had his 750 on the road for a few weeks, still prone to being way lean and cylinder #1 is not firing well (temp on the pipe is signficantly less than the others). Plus he has a valve cover oil leak, so I have his bike back for a bit more work. I found the "washer on the carb needle" trick online. It consists of adding #4 washers (1/8" ID, approx .030" thick) on each needle so it sits slightly higher in its carb, adding more gas all the way up off idle. I won't go into the details of pulling the needle assembly apart since thats all online, but I did find that using an 8mm socket on an extension (no wrench, only socket w/ extension, used as screwdriver) was helpful in removing the star retainers- DO NOT FORCE THEM, there is a spring detent which locks them in place, they only need slight pressure and rotation to unseat. The online source suggested 2 #4 washers per needle but I could only fit one on each- different thickness washers I suppose. The star retainer would not seat with 2 on the needle. I did notice a significant reduction in the lean bogging on subsequent startup, so its an effective cheap & easy improvement.

We got the valve cover off, waiting for the sealing compound to show up and then we'll put in his new gasket. He's going to bring over a compression tester so we can look into #1- we messed up the compression test first time- forgot to hold the throttle wide open, which restricts the air coming in so compression readings will be low. Ignition coil tests with a meter show it OK. The carb slide moves easily and it is clean.. hoping #1 doesn't have ring/valve issues but we'll see I guess.

Rebalancing these carbs is a pleasure, adjustment screws are easy to get at and conveniently located 10-32 tapped ports on the intake manifolds- very easy to hook up a manometer. I'll do his again after we get the valve cover sorted.

Happily he is using the bike cover I gave him- when heading out he takes it off and stashes it in his car's trunk :)
 
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