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Messages - K2-K6

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5161
CB500/550 / Re: good old fashioned british know how
« on: August 02, 2010, 08:44:40 PM »
As long as they close safely then it shouldn't cause a problem. Although it's difficult to judge it without looking at it.

The action is probably an intended difference in the carb design to give a quicker throttle action for their type of use (ie race orientated) with a standard type twistgrip, the cable can't change this.

This is a bit obscure but the original Honda pull cables had a nylon/ plastic internal sleeve inside that tight turn coming out of the twistgrip, not sure if the closing cable is also equipped. The effect without it is that you can have difficulty particularly when you start to open the thottle and the tension feels high friction so you struggle for any subtle control as you start to roll it on.

5162
CB750 / Re: Project bike
« on: August 02, 2010, 08:27:34 PM »
Good news, and well done. It's always easier if you end up without having to machine the thing to get the casting back to useful.

What catches out people on these is the sealant Honda used at the factory as it sticks so well but does usually end up with the stud having very little corrosion inside the casting wich is good.

Even if you intend to remove a complete stud from exhaust port most people go with the two-nuts method and they often snap just at the end of the threads anyway, so you have to make sure you get a good hold on the area below this to be able to apply enough torque to get a release of the sealant. Mostly vice grips don't work either as you can't get enough bite especially if the jaws are a bit worn.

5163
CB750 / Re: Project bike
« on: August 01, 2010, 11:22:43 AM »
A little bit more, I think the studs were originally put into the head with a sealant that is heat proof to prevent them backing out when normal removal / fitting of an exhaust takes place and it is this that makes them seem tight in the casting. This is why if you can get a good secure hold of them they will come out as it's like breaking a loctighted bond as opposed to rusted into the ali casting.

You have in effect got two seperate problems that you are encountering 1) the nut is siezed onto the stud from corrosion and breaks the stud. 2) only related because it is the same stud and not corrosion; is the original intntion to fit the stud securely to the head by Honda with whatever loctite type compound they used. You may even be able to get something that "unlocks" the original bond, but still have to grab the stud effectively enough to apply torque to it.

If the studs are reinstalled using copper grease, then quite often they come out of the head if you try to undo the exhaust clamp but it's no big deal.

If you wanted to avoid getting the nuts stuck in future then probably an annual remove and copper greas will do, same for the plugs as well particularly the centre two as they get the most water from the front wheel.

5164
CB750 / Re: Project bike
« on: July 31, 2010, 10:54:00 PM »
Hi Waggles

 I'd go at it like this:-

The main reason these break is that the nut doesn't reach the end of the thread and most likely has no grease either. Nut siezes, weak point where threads end snaps off as it's most likeley also been reduced at this point by by corrosion.

Soak in "Plus Gas" either by making a small captive bowl around it (body filler) and leave to soak overnight.

Then make a tool out of steel bar by drilling one end to fit over the stud and almost reach the head and file a hex shape on other end to take a socket / spanner. Then cut vertically into the stud end to the full depth of the bore, if you put it on the stud now you should be able to look at the stud through the slots just cut if that makes sense.

You then need to arc (plain arc / TIG are stronger than MIG) weld along the slots to attach to the stud along both slots, this distributes load along the stud and gets it through a heat cycle.

Leave to cool off then tweak it forward and back with a socket (six sided) to see if it will move, if it won't come out like this it's doubtful it would at all

 

5165
CB750 / Re: CB750 K3 Oil leak
« on: July 31, 2010, 10:20:03 PM »
SEP sounds like a good recommendation? I've no knowledge of them but it seems from what they have done for you that they can do the work to a level you need.

My reasons for being careful about skimming barrels is that they are hard to do correctly without some experienced engineering behind them, I've seen a few that have not been successful so If you can get this level of service it makes it much more of an option.

The cam chain comment I made is I believe relevant as if you consider when you adjust the drive chain you only make a small move in length but the slack changes out of all proportion to how far you've just moved the spindle. I'm not clever enough to do the calculation but it must have something to do with sprocket diameter, I don't think it's a straight no ratio effect though.

5166
CB750 / Re: CB750 K3 Oil leak
« on: July 30, 2010, 09:49:46 PM »
Seems like optimistic news so far. It's a good thread for anyone else looking in and working in the same area as I guess there are some relevant changes to consider since they were originally produced.

Thanks for considering our opinions of value, hopefully you get to enjoy it now.

5167
CB750 / Re: F2 carb flooding
« on: July 28, 2010, 10:07:54 PM »
Hi

The brass tube will normally be above the fuel level with a correctly set float and valve and so have nil affect on any carburation.

BUT........... if the bowl continues to fill the fuel now has (outlet blocked) no route out other than through the carb and depending on arrangement, angle, etc could fill the cylinder!! IF this happens the cylinder will not pass compression when cranked over and will most likely bend the con-rod. I think the tube is important so would install replacement.

Even if it kept getting a small amount of fuel into the motor it is still ultimately drastic if left unchecked, bore wear, oil dilution, leading to bearing / cam failure.

Not trying to scare you, as if all is well then nothing, but it is an important contingency.

Hope this helps.

5168
CB750 / Re: Fork oil
« on: July 26, 2010, 09:04:42 PM »
SAE 30 is about the pactical max before they start feeling harsh so take your pick. Think all the brands are quite good now but always used Bel-Ray in moto-cross as it stayed good during high demand / heat, but also like Motul.

It's good to have a bit of drop as you roll off the throttle for a corner as the head angle tightens on compression or else the steering feels even slower. I find if you go much over 20sae that starts to slow down noticeably and the steering start too feel odd:- forks go down slower so you feel initially that you have to turn it harder then compression peaks later and you start "thrupenny bitting", if that makes any sense.

Plus too high SAE and it starts to stutter on bumps as the bike rather than the forks move up.

5169
CB750 / Re: 750F2 First ride at last.
« on: July 26, 2010, 08:36:01 PM »
Sounds good, any pics for us to have a look at it?

They are a bit different to modern stuff, much longer and harder to change direction. They need some persuasive pressure that would have a newer race-rep straight upside down if used. It's much more like a big bore moto-crosser in that it's a lot of footpeg weighting and big pull of counter-steer to deviate it from straight ahead at speed, respectably quick though.

We had a small guy owned one early 80's and with ad-hoc drag racing (ahem, not on the public highway officer!!) that F2 would beat most things in it's era till CB900 Suzuki GSX etc came around.

Hope you enjoy it.

5170
CB750 / Re: soda blasting
« on: July 26, 2010, 03:26:18 PM »
That's a really good explanation of it, can you do your teeth while you're at it?

Looks like it will be ideal for quite a lot of bike components.

Also all the work place air nozels like that we had were removed by the elves of safety to reduce nozel pressure being dangerous!!! I guess they'll not even let us have compressed air at all in our bright new safe future.

5171
CB750 / Re: CB750 K3 Oil leak
« on: July 26, 2010, 03:15:52 PM »
Here's a slightly different angle on it which may explain some of the experience old-v-new gaskets etc.

This era or production has covered the removal of asbestos from head gaskets so any original specs that used it would have to have been re-formulated. Commonly they went from asbestos to graphite and one of the characteristics that changed was it was more common for liquids to creep through the new ones, making it common practice to have a sealant where none was needed prior to this.

Graphite type gaskets also need retorqueing on some arrangements also and this is never part of the plan for SOHC 750 motors due to the need to remove from frame to work on. I'm guessing this but it may be why they are more succesful with sealant with the types available now both Honda and pattern.

There is a piece written in current "Classice Bike" along these lines, not specfically dealing with this application but if you overlay the info contained with our experience and the timeline involved I think you can form a more thorough resoning as to the use of sealant or not.

I guess this impacts many of the bikes on here.

5172
CB750 / Re: soda blasting
« on: July 25, 2010, 08:06:44 PM »
Oooooh don't know about that, but it is alkaline isn't it? so should have some positive effect of corrosion and inhibit a furry recoating afterwards.

Don't know if that will impact of eventual re-coating of pieces.

5173
Misc / Open / Re: This weekends pictures (Not a lot of SOHC content)
« on: July 25, 2010, 07:59:59 PM »
Thanks for the effort of posting all that, really good. Seems that you had a good weekend out.

I guess I should say Cheers!

5174
CB350/400 / Re: barn find
« on: July 25, 2010, 07:53:05 PM »
I now it's a lot of work to go but it feels really nice to get those black bits back all nicely finished, looks like quite a nice finish as well.

5175
CB750 / Re: CB750 K3 Oil leak
« on: July 25, 2010, 07:46:38 PM »
Hope you've got it with that, it's nice when they run well and you know you can get a reliable run out on it.

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