CB750 DOHC Fork Interval Question(New problem updated)

Gottcha. Now in theory, both fork legs would fully extend under gravity and the axle would be a straight bolt in. So is the wheel on the deck and pushing up on the right fork leg and that's why that leg is shorter than the left? That would explain everything.

Maybe as a simpler next step, make sure the bike weight is supported and remove the front wheel. Then slip the front axle in and see if it sits where it's supposed to be with no load on either leg. If the axle isn't a slide it fit, then the fork legs have to be checked. You can start by making sure that the tops of the legs are equal distances above the top triple clamp.
If they are and the legs overall are different lengths, they have to be removed and stripped to work out what's missing/wrong.

If that's OK, then try to refit the front wheel without any load on the front end and see if it's OK.
 
teazer said:
Gottcha. Now in theory, both fork legs would fully extend under gravity and the axle would be a straight bolt in. So is the wheel on the deck and pushing up on the right fork leg and that's why that leg is shorter than the left? That would explain everything.

Maybe as a simpler next step, make sure the bike weight is supported and remove the front wheel. Then slip the front axle in and see if it sits where it's supposed to be with no load on either leg. If the axle isn't a slide it fit, then the fork legs have to be checked. You can start by making sure that the tops of the legs are equal distances above the top triple clamp.
If they are and the legs overall are different lengths, they have to be removed and stripped to work out what's missing/wrong.

If that's OK, then try to refit the front wheel without any load on the front end and see if it's OK.
Click to expand...

Thanks for the precious advice. I will start figuring out where the problems are tomorrow and post the updates here.
 
Ok, I disassembled the whole fork and made sure everything was assembled right. Fork tubes look straight(they should be as they are new), springs are new, the two forks' length look identical.

But after I mounted them onto the triple clamps, they don't look parallel. Tried to mount the front wheels again and didn't sitting on the axle right just as before.
I took the front wheel axle out and used it as a ruler, not surprisingly, the two half moons (the bottom end of the forks) are not sitting on the axle right - the interval is too short to fit them right.

Now the triple clamps look suspicious...
 
I really suspect that your upper and lower triple trees do not match. Are they both original? I think that you mentioned powder coating. Is there a chance the PC shop switched one with another customer by accident?
 
pidjones said:
I really suspect that your upper and lower triple trees do not match. Are they both original? I think that you mentioned powder coating. Is there a chance the PC shop switched one with another customer by accident?
Click to expand...

They are original. I will try to clean off the inner surface with some paint stripper and see how would that go.
 
OK, so let's test the hypothesis that the triples are damaged.

Measure the distance between the chrome legs just under the top triple and again at the lower triple and just above the sliders. All three measurements should be exactly the same.

Next, take two lengths of angle (iron or aluminum) or dead straight tube. Place one above the lower triple and retain it by hand or lightly with a bungee cord or similar. Them take the second one and place it on the fork legs resting on the fork oil seals and against the legs.

Now look down from above and see if both rods are dead straight. Your eyes can detect an out of parallel situation of less than a degree if you look carefully. Look down at them so that one disappears behind (below) the other and you should see any errors.

You could also look at the forks from the side and see if the two legs are parallel. It should be fairly obvious if they are not.
 
teazer said:
OK, so let's test the hypothesis that the triples are damaged.

Measure the distance between the chrome legs just under the top triple and again at the lower triple and just above the sliders. All three measurements should be exactly the same.

Next, take two lengths of angle (iron or aluminum) or dead straight tube. Place one above the lower triple and retain it by hand or lightly with a bungee cord or similar. Them take the second one and place it on the fork legs resting on the fork oil seals and against the legs.

Now look down from above and see if both rods are dead straight. Your eyes can detect an out of parallel situation of less than a degree if you look carefully. Look down at them so that one disappears behind (below) the other and you should see any errors.

You could also look at the forks from the side and see if the two legs are parallel. It should be fairly obvious if they are not.
Click to expand...

I measured it. The distance between triples and between the lower triple and the top of the dust seals are exactly the same, if not close enough. Also they look pretty parallels without bending to my eyes. Could it be wrongly assembled front wheel axle ? I'm no expert to this bike as it's my first ever build, I'll upload some photos for your reference.
 

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That looks OK.

So let's try something else.

Remove the front axle from the wheel and then place it in the forks and bolt up one side end cap. What is happening on the other fork end cap? If it's up tight against the lower face of the leg, then that's not the issue.

By any chance does that speedo drive have a locating peg that matches a slot on the slider? It's possible that the drive gearbox is hanging up. If the gearbox can't slide into place, that would cause the problem. I want to say that teh 900C gearbox has a slot that matches a peg on the fork leg, and the F has a peg on the box, but check what you have and try rotating the gearbox a few degrees either way and see if it goes into place.
 
teazer said:
That looks OK.

So let's try something else.

Remove the front axle from the wheel and then place it in the forks and bolt up one side end cap. What is happening on the other fork end cap? If it's up tight against the lower face of the leg, then that's not the issue.

By any chance does that speedo drive have a locating peg that matches a slot on the slider? It's possible that the drive gearbox is hanging up. If the gearbox can't slide into place, that would cause the problem. I want to say that teh 900C gearbox has a slot that matches a peg on the fork leg, and the F has a peg on the box, but check what you have and try rotating the gearbox a few degrees either way and see if it goes into place.
Click to expand...

I tried it. One end of the axle is sitting right in the halfmoon while the other end is not sitting right. The other halfmoon will be sitting on the hex shaped section of the other end of the axle(forgive my poor English...), so it looks like the axle is too long for the fork legs interval
 
The part with the hex shape (the axle nut) is clamped by the fork bottom clamp FIRST. Then the other end SHOULD fall tightly into the other fork half-moon. On many Hondas, there is a mark around that end that should be approximately at the edge of the fork. Really, placing it in exactly by the FSM (they are available online) is what you should be doing - and placing a printout of the instructions where you can find it again, because you WILL need them again.
 
He's right that the FSM should help, but I am surprised that the axle looks to be too long. Did that wheel come out of those forks originally or did it come form a different bike? It's not from a 900C model or something else is by any chance? I don't know what differences there are but the FSM for 900C shows the sleeve nut on the left (speedo drive) side and it shows the sleeve nut on the other side for early 750s.

Make me wander if the forks are different or wheel spacers and axle are different between different models.
 
I have read the FSM several times to make sure everything is assembled in the right way, but there's must be something I was missing.
After several days of cursing and trying, I still couldn't figure out a way to get them sitting right, it's frustrating.

Can anyone help me to measure how far does the front wheel axle pokes out from the front wheel? If the distances are identical, I can eliminate one more possibilities from my list...but right now I think something is wrong with the triples.
 
Simple answer is that the axle should not stick out like that.

Measure the for spacing just below the top triple clamp, just below the lower triple and just above the fork sliders. Those 3 readings should be identical. Forget about the gap between the sliders for now. Let's take care of basics.

Did that wheel come with the bike when you bought it (and was it fitted)? Any pics of the front end when you bought the bike?

Where are you located? Maybe someone lives close enough to take a look at it for you.
 
teazer said:
Simple answer is that the axle should not stick out like that.

Measure the for spacing just below the top triple clamp, just below the lower triple and just above the fork sliders. Those 3 readings should be identical. Forget about the gap between the sliders for now. Let's take care of basics.

Did that wheel come with the bike when you bought it (and was it fitted)? Any pics of the front end when you bought the bike?

Where are you located? Maybe someone lives close enough to take a look at it for you.
Click to expand...

The axle was the original one that I took off the bike. That being said, I did take the whole front wheel to a shop to have them fabricate the spacer collar, so they might mixed it with other parts. I have looked on eBay and found that my axle is actually too long for the same year and model. I ordered one used parts from eBay and it is arriving on Saturday, let's see how would that go.

I live in the LA area and would appreciate if anyone close could come over and check on it. If anyone feels like to, please DM me!
 
Re: CB750 DOHC Fork Interval Question(SOLVED!!)

I solved it!
Up: my previous axle
Down: new axle bought from eBay

Turns out that my axle isn't original lol. I put the new one on and it's perfect! Thank you guys so much for helping me!!
 

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