Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: El__burro on April 23, 2016, 02:45:50 PM
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Good day,
Today I have taken the bike (k2) for a test ride.
Still need to adjust a few things.
1 The bike runs fine on the first part of the throttle then it struggles (unless I open the throttle very gently)
2 Both front and back end feel not stable (quite stiff).
3 At traffic light it's quite smokey.
4 After replacing for the 3rd time both oil seals the RH side fork still leaks.
these are the issues I would like to sort out first.
Can you help?
El__burro
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Good day,
Today I have taken the bike (k2) for a test ride.
Still need to adjust a few things.
1 The bike runs fine on the first part of the throttle then it struggles (unless I open the throttle very gently)
2 Both front and back end feel not stable (quite stiff).
3 At traffic light it's quite smokey.
4 After replacing for the 3rd time both oil seals the RH side fork still leaks.
these are the issues I would like to sort out first.
Can you help?
El__burro
do a plug check at mid-range ,is it lean ? or sootty ?
try thinner oil in the forks,at the rear,can you soffen the spring pre-load ?
the smoking may be due to mixture issues
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I have not managed to do far another ride yet,
Tomorrow (if weather is ok) I'll check the plugs.
Fork oil is as suggested by manual and leaks from one fork only.
Thanks
el__burro
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From past experience, if a fork leaks even after new seals then it often means that the fork leg has some pitting or scores somewhere in its travel. They can be very very small and hard to find.
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From past experience, if a fork leaks even after new seals then it often means that the fork leg has some pitting or scores somewhere in its travel. They can be very very small and hard to find.
This morning I have re re replaced the seal on the right hand side.
At first inspection it holds fine. Hopefully it will stay that way
otherwise I will look for a replacement part.
Thanks
el__burro
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From past experience, if a fork leaks even after new seals then it often means that the fork leg has some pitting or scores somewhere in its travel. They can be very very small and hard to find.
You were right, After I replaced 3 seals, it still leaked, once I replaced the stanchion it is sorted.
Thanks
el__burro
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In regards of the test ride, the bike struggles when I open the second half of the throttle.
Below is one of the plugs I checked this morning.
What shall i look for?
(http://uploads.tapatalk-cdn.com/20160521/8fe9d7995902d0e865715fcf98ca90b1.jpg)
Thanks
el__burro
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That plug looks like it fouled up mate, its running far too rich, the plugs should be a greyish to light brown, if dark brown, or black like it is now I would sling them get a new set but before fitting them weaken the mixture, because its running far too rich try one full turn on the mixture screws & give it another run
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As above, the plug is showing far too rich a mixture compared to what it should look like as I've always worked toward pale milk chocolate colour as being close to correct mixture.
There is a big qualifier to that though, the engine should be warmed to normal operating temperature and then you'd get it pulling hard in something like third gear and fairly well up into the Rev range I.e. full throttle, then cut the motor and coast to a stop. Only then pull their plugs and check the colour to see what the main jets are letting the mixture run at. Once you get the main jets right you can fine tune with the needle position and air screws to fit the lower regions around that.
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Tried that on my T250, unfortunately the ignition key is below the petrol tank (and no engine kill switch fitted), damn near crashed trying to reach the key! 😀
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.. UPDATE ..
after cleaning all 4 spark plugs and giving the carb mix screw a full turn out (from all closed) it did run slightly better, eventually once i checked the plug after a 10 minutes ride they were as dark and fouled as before( as per img above).
Shall i open or close the mix screw?
Something that concerns me is that when I am in a bend the front of the bike wobbles a bit.
I checked all the connection and the wheel is properly installed.
no play at fork level either.
Any ideas?
Thanks
el__burro
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try another turn out,and see what happens,
as for the wobbles,all bike have a slight wobble around 40 mph,but should be okay with both hands on the bars,
check the steering head,make sure its not to tight ,
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all bike have a slight wobble around 40 mph,but should be okay with both hands on the bars
Thanks, actually the wobble happens at 10mph too
I'll give the 1/2 turn a try tomorrow
el__burro
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Go for 1/2
Then 1/2 again if needed.
The wobble sounds like
the headrace is tight. Try
to loosen 1/4 turn
Sent from my SM-G361F using Tapatalk
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What's the headrace?
Thanks for your help
el__burro
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What's the headrace?
Thanks for your help
el__burro
the long stem that swivels the forks in the frame,it should be be almost a gentle fit,defo not loose,but to tight makes the steering iffy
https://www.google.co.uk/search?q=motorcycle+headstock&biw=1366&bih=643&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwj74YG9g8jNAhXnJMAKHegiBxYQsAQIGw
see pics
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so, remove the top joke and loosen the bolt (no 6 in the image)?
Thanks
El__burro
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No need to disturb the top yoke, get a C spanner (similar to the one for adjusting the rear shocks) and it can be accessed, or you may be able to tap it round with a punch.
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Are you sure it is the head bearings ? If you have done it café style by lowering the front end and longer shocks on the rear, you have altered the rake and it will wobble in a bend and at high speed.
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You do not need to remove the yoke but you do need to loosen the top nut and the two pinch bolts on the yoke at the forks to allow everything to move easy
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Latest update
I have followed your instructions and have losened the nut as suggested, went for a ride and I felt a better handling unfortunately I could also feel some play in the tree area going over speed bumps.
I tighten it a bit towards a stiffer ride for now.
How loose should it actually be?
Thanks
el__burro
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loose enough for easy movement,but no play !!
can you raise the front end ?? so you can turn from lock to lock,and also try and lift op and down the forks ,see if you feel any movement,
https://www.youtube.com/watch?v=Fi_fmONC9Jg
this video may help
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no improvement on the 2 issues.
A) The engine struggles on the second part of the throttle
B) The bike seems a bit too stiff on the front end.
a) I have changed the airscrew mix setting of the carbs a few (hundreds) times but its not getting better.
I should mention that I have replaced the (stock) air filter with air cones.
The spark plugs are carbon fouled (see picture in previous post).
Is there anyway to check which carb is at fault. I have managed to sync the carbs.
b) Probably best solution is to replace top and bottom bearings, any advice on shopping?
Ps I have mounted clip ons.
Thanks
el__burro
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the plugs read over rich,try it without the aircleaners on,
also,check the ignition timing,it could be retarded,
the air screws on control the first 1/4 of the throttle,
as for the front seeming stiff? heavy ?
check your tyre pressures,
try thinner fork oil,remember,with clip-ons,you won't get the leverage of wider normal bars
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I have probably mentioned a few times before but..
I replaced the stock air filter with some pods.
could this be the cause of the poor running.
(when I pull the second half of the throttle).
I have adjusted the timing (which was ok)
I will be sincronisyng the carbs next.
I was just thinking about re jetting.
Could this help?
Another hint is that the 2-3 plug look very close to perfection
while 1-4 look very carbon fouled.
el_burro
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Sorted one issue..
I have cleaned and synchronised the carbs, set the floats to spec, adjusted the timing, adjusted the valves gap, I've gone for a ride and..
GREAT, no more struggle at half throttle.
My other issue is still there though, steering is a bit stiff/wobbly.
Tried to loosen/tighten the head race, tyre pressure is ok, front wheel is ok..
Probably replacing top and bottom bearings could be a good idea.
Any suggestion? (how many balls does the top bearing have 18?)
Thanks
el__burro
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Far easier to use taper roller bearings than separate and fiddly balls! Not a good idea to replace just the balls, the tracks/races would need replacing as well to do the job properly, otherwise it would be like fitting new shells to a knackered crank, a lot of work, that wouldn't last long!
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I am trying to find out what "tracks/races" are exactly.
in the meantime I have put a set of roller in my basket.
Thanks
el__burro
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The tracks are the bits that the balls run in, a sort of half circular ring of metal, but the roller bearing set you have ordered contains everything you need to do the job.
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..so just the full set in my basket will do,
no other parts are needed to move from the 18 balls bearing to the new one?
Thanks a lot
el__burro
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That is correct, and they are so much easier to fit than loose balls, especially the bottom set!
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while I wait for the bearing to arrive, I have removed the old ones.
I had 17 balls on the top bearing and 15 on the bottom.
Hopefully this was the cause of the problem.
Until next update...
el__burro
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actually the set arrived just now.
anyone able to tell me in what order they go.
(http://uploads.tapatalk-cdn.com/20160921/c888f5e4775c5010226d607c7bfb8751.jpg)
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From the photo it looks like bottom row right into the bottom of the frame (headstock) and the bottom middle onto the base of the steering stem BUT you'd have to get the seal on there first as it should turn and seal inside the frame aperture to prevent anything entering the bearings.
It's hard to see exactly which way the seal goes in without being there so you'll have to assess that yourself.
Once you get both of the outer tracks into the frame and seated, you can push the steering stem into place and drop the top bearing into place. It looks as though you've got a dust seal for that end too so youll have to test fit it too see how it goes but looks from the photo to be cup side down. There is a chance that it's supplied with two seals to give an alternative fit to the bottom and none at all at the top, again, you'll have to decide what is what.
You can then put the top yoke on with none of the pinch bolts done up. Then tighten the main central clamping nut at the very top up to about 30lbs of torque while moving the steering left to right, this will pull the bearing seats into the frame properly. Then undo the nut and relighting to about 5lbs, this should set the steering to a very light smooth movement without slack left in it.
Then you can build the fork legs back into it for final assembled.
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i am looking at different videos and it seems like they all fit a thicker washer under number 4 rubber seal. (see picture above)
the old one i have is pretty thin, would it be ok?
thanks
el__burro(http://uploads.tapatalk-cdn.com/20160922/7b1ebdfdf37f0740b28dc8a7f8b189c9.jpg)
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The. Original kits (years ago) used that thick spacer with a seal round the outside of it but I can't remember why they had that, it may have been to bring the total bearing dimensions back to the same spec as the original fitment in terms of ending up with identical geometry to the factory bearings.
It's slightly difficult without being there in front of it but loosely I think this is what happens: the new roller bearing if put onto the stem without a spacer will move the whole assembly up into the bike so that when you put the top yoke on it will end up closer to the bottom one and to then get the fork legs level with the top yoke you will have to drop them relative to the bike which will lift the front of the frame. I know it sounds convoluted but they were trying to absolutely preserve the original geometry.
Technically speaking it shouldn't compromise the integrity of the assembly if you go without the thick spacer but you will get a minor change in steering geometry but no more than using a slightly different sized tire. Really in most cases a good setup with roller bearings is going to be much better that a worn original setup anyway.
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You probably know anyway but..... Use the old bearing shells to tap the new ones in place as they're the same diameter.
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Hello everyone,
going back to steering issue, having replaced the bearing hasn't improved much.
Looking at the bike it seems like the problem could be the electric cabling going to the headlights.
I feel friction when I turn right (so the cable gets stretched) and when I turn left i have the cable holding the movement.
I am trying to see the best routing option.
As per image attached, I have passed the (probably too big) bundle of wires just under the tank holder.
Is there a better way.
thanks
El__burro
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:-\ why have you got that switch there ?
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it's the kill switch.
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Sorted, it was the bundle of cables too large,
I removed a layer or 2 of the shrinking tube and now it has free movement.
Thanks.
el__burro (http://uploads.tapatalk-cdn.com/20161005/b993dcdd2541a9be7070a23097097c54.jpg)