Advice appreciated

[Fairview]

Hi, I have recently acquired a CB550 k1 as a rolling (light) renovation project. Initial impressions of the bike have been good but I hoped to benefit from the combined wisdom of forum members regarding a couple of pressing issues, I'm not hugely mechanically knowledgeable.

The first is a running problem which I think is a misfire noticeable from about 3000 revs up. Having just returned from a 120 mile round trip the problem was most noticeable on the motorway where max possible speed was about 60mph (speedo wavering between 40 and 80mph), engine sounded lumpy especially up-hill where lack of power was very noticeable, you know things aren't going well when you re overtaken by a string of artics. Fuel consumption was poor (30 odd mpg). At low revs performance isn't noticeably effected and she can be coxed up to red line without too much trouble in low gears. Starting is always great, single kick hot or cold, tick over isn't bad but engine has to be fully warm for it to settle. I'm not sure if it's relevent but it only needs choke for a few seconds when cold, and on inspection this evening the plugs are a little sooty. I put some premium unleaded in it and for a while it seemed to run a bit better but soon went back to it's bad ways. I know it could be a hundred things but if anyone has got any suggestions of where I should start I'd be grateful. It has had a recent service, still waiting for a new air filter bu the existing one has had a blow through.

The second less important problem (if anyone's still reading) is the throttle control. Despite being free moving, gripping and holding the throttle open for more than five minutes at a time is cramp inducing agony. Not sure if its down to the shiny hard grip or if there is any other means of improving things. It doesn't sound much of a problem but I'm not exaggerating when I say it made the long ride flipping hard work, especially coupled with the lack of power.

Thanks

[LesterPiglet]

Who did the service and what was serviced? It may be running rich by your description and the fact that it's an old air filter. Try running it without the filter and see if it improves any.
Remove the second (closing) throttle cable if it is still there, it isn't needed.

[Bryanj]

Done a full 6,000 service with new plugs, plug caps and possibly points? or just a 1500 oil change?

What exhaust system is it running?

K1 and 2 don't need much choke it's the K3 thats cold blooded.

Sorry Lester but both cables ARE needed (Try stopping one with the throttle stuck open!!) but new cables and grips will probably help

[SteveD CB500K0]

The throttle spring is very heavy on the 500. We just lived with it...

Easy starts, quick off choke, lack of top-end power sounds like rich running.
Do a plug chop on full throttle and see what colour they are. Plenty of instructions for how-too if you search on here.

Steve

[florence]

Rich running definitely.  Check that one or more of your carbs isn't flooding; this would give the all symptoms you describe. 

[LesterPiglet]

Never used the second cable...I have a kill switch.

[hairygit]

Not using the second cable can put you in a very sticky situation if the opening cable is stiff or should stick. A kill switch might save the engine from blowing, but you will have no engine braking, the bike will be freewheeling and infinitely more difficult and dangerous to stop under full control, never a good idea on a 2 wheeled vehicle!

[matthewmosse]

It doen't make the throttle any heavyer to operate, and besides being very handy to prevent throttle sticking open - more common then you might think especially in frosty conditions and bikes that sometimes live outdoors, I also have on occasion had to swap the cables over when the pull cable snapped on me. I'd go over all the controlls with lube to see if any inprovement, possibly consider thicker / larger diameter grips which would give mor leaverage and the main thing I did thinking back on my early 500/4 years was to fully master the art of rolling the twist grip open with my wrist not having to change angle as I think it's holding your wrist at an angle with force rather than the actual force required that causes wrist ache. I'm not sure if my expanation is entierly clear but have a go at rolling the throttle open with your fingers and then holding it there with your palm and relaxing the fingers again, after a while it's second nature and you forget the throttle is heavy. As with most of these things there is a technique that once learned is usefull for further riding on a whole range of machines, I've recently started to do some greenlaning as a job and a lot of the things my 500/4 taught me are quite usefull to offroad riding, that throttle controll method and the other is to very lightly feather the brakes, without fully applying them using 1 or 2 fingers whilst riding otherwise normally, on the 500/4 I did this too keep the front disk dry in really torrential rain, especially on motorways where you'd go miles without using brakes so they'd get very cold and wet and loose effectiveness.

[LesterPiglet]

This is the only bike I've ever had with two cables so I think it's more of an H&E exercise. I shall be looking into lightening the throttle by way of a softer spring or something. Sorry for the hijack.

[totty]

Assuming everything is in good condition and working correctly then try one of these on the throttle
http://www.mandp.co.uk/productInfo.aspx?catRef=503589

Soft grips with a deep pattern can also help.

[Fairview]

Thanks for the replies everyone. I'll whip the filter out tomorrow and try it, seems too simple for my luck but you never know. If not I'll try the plug chop and see what that shows. The flooding float chamber sounds like a possibility, it's had new plugs etc. It's still running on the original 4-4 exhaust but they are tired and patched. I need to decide on a suitable replacement as not sure i can stretch to the Dave Silver 600 quid OE replacements (any opinions). That wouldn't be effecting things presumably?

As for the throttle - there seems to be varied opinion on this, the strange thing is I've got a TDM and when compared with the CB it doesn't seem to be much difference, both have double cables too. The TDM has soft rubber grips though. I accept that it might be down to technique and will give what Matthew suggests a go,  but don't think it is just a case of getting used to it, I've had plenty of bikes but never had this problem. The wife rides it too and can't see her enjoying the ride with this set up. That gadget that Totty suggested might do for her.

Thanks again everyone who has replied- I'll update later.

[LesterPiglet]

I got myself a chrome Motad replacement exhaust. I didn't find anything else made for it at the time. Nice pipe tho I wish it was a bit shorter.

[jcknapp]

First thing I would do is a carb rebuilt kit. Really inexpensive and the carbs probably look like toilet bowls anyways. They I would check the jet size for the main and the pilot. Should be around 100 maybe and maybe 38-40 for the pilots. Run the engine and I got some great advice here for checking the fuel/air mixture. Run the engine hot for 10-15 min. kill the engine, pull the plugs and check the bottom. I would start here. I've realized since I have been riding motorcycles its all about the carbs!!!!! I am dialing mine in right now after adding velocity stacks and rejetting but thats a whole different project.    I used to get cramps on my throttle too. I got used to it by building in up the muscle (haha) or you could get a cruise control bracket for a few dollars when you're on the highway. Also I would do what Lester said and check the filter. There are some improved AM filters for this bike that are much better than the stock ones. Try ebay. Also what matthew said about the hand placement and movement on the throttle is excellent. I gradually roll mine all over in front and back making the muscle not so stressed and more comfortable and enjoyable to ride. Hope some of this info helps!!!

[totty]

If your air filter is past it consider replacing the paper element with filter foam from RamAir, it cost £9 for enough foam to do 2 or 3 filters and they can be washed, they sell direct on ebay. It's a very easy job with a knife and a glue gun.

[Tomb]

A kill switch might save the engine from blowing, but you will have no engine braking, the bike will be freewheeling

Freewheeling?? why?    ....I'm confused, surely if your engine is in gear with throttle stuck open and the kill switch is turned the bike just slows down like you've shut the throttle.

I know what you mean about throttle slides freezing, if I have had to ride in heavy snow (in the past, too old soft now ) I've used my old CB550 with sidecar and had the slides freeze open, had to get home using the kill switch as an on off throttle.

My 500/4 cafe has a Tomaselli quick twist which only has one cable which has been Ok.