Author Topic: CB 750 Project 1 - Rides Well but a few tweaks needed (Read 114283 times)

colined2 · « **Reply #375 on:** December 02, 2015, 03:31:57 PM »

Tim me again
The replacement studs for the cam tower bolts are 6x65mm.Honda part number #92700-060650B (4 of)
The replacement studs that go under 4 of the rubber discs under the cam tower are 6x50mm. Honda part number #92700-060500B (4 of)
The replacement stud for rear of cylinder is 6x50mm.Honda part number #92700-060500B. (The same as above).
The replacement stud for front of cylinder is 6x102mm.The Honda part number is #92700-061020B. Good luck finding this one. I know that a certain model Kawasaki KVF400 uses this size but I could not find the part number,you might have to ring around or spend some time on the internet looking for one. I was lucky and found a good secondhand one.
Hope this helps.
Colin

timbo750 · « **Reply #376 on:** December 02, 2015, 03:33:30 PM »

Colin. That's awsome. I will let you know how I go.

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timbo750 · « **Reply #377 on:** December 02, 2015, 07:40:19 PM »

Got them all ordered including enough for the next engine. They all needed to go on back order so hopefully have them in 2 weeks.

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timbo750 · « **Reply #378 on:** December 02, 2015, 07:51:36 PM »

Also ordered flange nuts while as well. I will try to get all the engine and covers painted while I am waiting for these.

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timbo750 · « **Reply #379 on:** December 03, 2015, 04:12:21 PM »

After looking closely at photos of Colins cylinders and head I realised a difference in the cylinders. Mine will not take small rubber dowels/sleeves around some of the studs. I know that this was not on the original K0 but did it also disappear on later model engines?

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Terry in Australia · « **Reply #380 on:** December 03, 2015, 11:00:13 PM »

You've got an early top end on your engine Tim, I picked that when I saw your valve guides without valve guide seals, I'm not sure when they discontinued them, but I'm guessing K1 or very early K2. Same for your cylinder block, later (K3 onwards, but of course we didn't get K3-K5 in Oz, we jumped straight from K2 to K6) cylinder blocks had bigger dowels and seals than on the earlier engines, to stop any possible oil leaks.

As you've seen, the CB750 "evolved" over it's 9 year life, I can't remember how many subtle mods there were, but there were a lot. No biggie, if you torque your head properly, then re-torque it again before you install it, it won't leak. Cheers, Terry.

timbo750 · « **Reply #381 on:** December 05, 2015, 02:20:39 PM »

Thanks Terry. I was considering changing the studs and nearly did but I shied away for fear of breaking one and having to get it machined out. Now I am wishing I did so I can torque without fear of a leak.

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timbo750 · « **Reply #382 on:** December 09, 2015, 09:05:31 PM »

The other thing I would like to do before assemply is straighten a fin on the head. Its not baddly bent but I am painting the head and cylinders black and would like to sand the fins back and the bent fin is at one of the front corners.
I was thinking of warming the engine in the oven to about 70 to 80 degrees C. They try to manipulte the fin with additionalheat from a heat gun. If the chance of breaking the fin is too high then I wont try, so someone please let me know if I should not try this method.

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Terry in Australia · « **Reply #383 on:** December 09, 2015, 11:35:26 PM »

Best of luck with that Tim, the fins on our engines are usually very brittle, and require way more heat than that to make them soft enough to manipulate.

I heat cylinder blocks to around 200 deg C to pop out the sleeves and I can tell you that's not even close to hot enough. If you've got an oxy/acytelene torch (not just a gas torch, you need the oxy to increase the heat to soften the alloy) you can give it a go, but be careful even then, you could do more damage than good. Sucks, don't it? Cheers, Terry.

timbo750 · « **Reply #384 on:** December 09, 2015, 11:38:44 PM »

I thought it was a long shot. I was of the thinking that the bent most likely happened when the engine was hot and got knocked and that the end of a fin would only be about 100c.

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Terry in Australia · « **Reply #385 on:** December 10, 2015, 02:21:27 AM »

Yeah, it always surprises me that you can bend a fin by accident that will then break when you intentionally try to straighten it. Yes I understand that some metals become more brittle the more you try to manipulate them, but even so.......

timbo750 · « **Reply #386 on:** December 10, 2015, 02:27:04 AM »

I think part of the problem with aluminum is that it stretches. So in theory the long edge of the bent piece is stretched and will never go back to were it was. So when you try to bend it back under different conditions it cracks. And to top it off the cast aluminum is usually not malleable.

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SOHC4 Cafe Racer Fan · « **Reply #387 on:** December 10, 2015, 11:51:55 AM »

Quote from: timbo750 on December 09, 2015, 09:05:31 PM

The other thing I would like to do before assemply is straighten a fin on the head. Its not baddly bent but I am painting the head and cylinders black and would like to sand the fins back and the bent fin is at one of the front corners.
I was thinking of warming the engine in the oven to about 70 to 80 degrees C. They try to manipulte the fin with additionalheat from a heat gun. If the chance of breaking the fin is too high then I wont try, so someone please let me know if I should not try this method.

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I think you'd have to get it WAY hotter to where it is glowing red.

Terry in Australia · « **Reply #388 on:** December 10, 2015, 05:55:04 PM »

I've got a MIG welder with a spool gun set up just for welding alloy, it actually works really well on busted CB750 cases, but when I've welded aluminum, I don't remember seeing it glowing red like steel does? I remember reading up on welding aluminum and they talked about a "straw" color when it's at welding temp, I think if you waited for it to glow red, it might melt? Cheers, Terry. XXX

calj737 · « **Reply #389 on:** December 10, 2015, 06:09:44 PM »

You will notice from this picture that the 6061 tubing is not changing colors

Nor is it here while being TIG welded

Terry in Australia · « **Reply #390 on:** December 10, 2015, 06:52:00 PM »

Yep, the "straw" color is just a slight yellow shading, from memory.

timbo750 · « **Reply #391 on:** December 12, 2015, 05:17:31 AM »

Ok then. I am am going to try and straighten the fin by heating it to an almost straw colour and applying gentle pressure to the appropriate area. Wish me luck.

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calj737 · « **Reply #392 on:** December 12, 2015, 08:50:20 AM »

As aluminum turns "gold or yellow" it is quickly approaching the point where it will melt away and fall off. Heat it, add some pressure, keep heating with pressure until it moves under pressure. Avoid heating until a "color" then pressuring.

Terry in Australia · « **Reply #393 on:** December 12, 2015, 03:40:43 PM »

Just don't add too much pressure before the metal is ready to bend back, or it'll snap.

timbo750 · « **Reply #394 on:** December 12, 2015, 04:23:12 PM »

I am thinking of a clamp with a small amount of weight then apply heat . That way I am not going to get too heavy handed on it.

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timbo750 · « **Reply #395 on:** December 12, 2015, 06:58:39 PM »

Whilst doing final prep on the cylinders, I realised that my gasket kit does not have the o'rings that around the base of the sleeves. Can anyone tell me what size they are or should I just place another order with Yamaha?

timbo750 · « **Reply #396 on:** December 12, 2015, 11:22:05 PM »

Found out the size on the Yamiya website and they are not cheap. Over $6 each has made me look for the locally but having trouble. How do I tell if the o'rings I have are still ok or need replacing?

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timbo750 · « **Reply #397 on:** December 13, 2015, 06:55:21 PM »

found the bloody o'rings. In a separate bag that ended up underneath some other stuff, glad I didn't order them.

Terry in Australia · « **Reply #398 on:** December 14, 2015, 12:38:20 AM »

No worries Tim, from memory again, they're not your usual O rings, so I'm glad you found them. I like your idea for bending the fin back, keeping in mind that you'll need to have some sort of "block" to stop if from bending too far past horizontal. Cheers, Terry.

timbo750 · « **Reply #399 on:** December 15, 2015, 06:38:14 PM »

Got the cylinders on yesterday, very happy to see that. Realised afterward that I forgot to fit the cam tensioner and guide, I am hoping that I can raise the cylinders a bit to fit the guide and the tensioner will go on from the top. Fingers crossed.

I am also rethinking the straightening of the fin, the only reason is because of how close it is to the vertical metal rod and that it is most susceptible to splitting.

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Author Topic: CB 750 Project 1 - Rides Well but a few tweaks needed (Read 114283 times)