Honda CB250RS kickstarting difficulties

[Wilburtron]

Hello,

I'm having difficulties kickstarting a 1981 Honda CB250RS.

I finally got round to taking and passing my test a few months ago after, boh, over 8 years!! just pottering around on my 1973 C50. I bought a 2004 CBR125 2nd hand to do this, I kept that for a while but have now replaced it with the above. The 250's only done 17000 miles and is in (seemingly) excellent condition.

When I picked it up from the guy I checked first of all whether it was warm (and so potentially masking any starting cold problems) and then asked him to start it, he did this 2nd kick, no problems, though I think he recommended that it needed a little throttle generally, (couldn't really hear over the noise of the exhaust in the garage) - although I thought the CB250RS had some nifty little thing that circumvented the need for a little throttle)

This was 22nd March. I brought it back home that evening and managed to start it after 6 or so kicks. However as this was late and right next to people's windows and the exhaust is custom and rather loud I didn't keep it going for more than a minute.

Having finally got it taxed and insured and some time to go out on it, I just tried to start it this afternoon but couldn't.

I turned the fuel valve on, ignition on, into neutral, engine stop switch to RUN, choke fully pulled out, hand on front brake, no throttle, straddling the bike I gently pushed kickstarter until I felt some resistance, then gave it a hard kick, but nothing. Tried a little throttle for a couple of times, nothing, very briefly did I get it started after about 30-40 attempts, but although I started revving it and was seeing around 5-6000rpm it died on me after about 10 seconds. Should I have really revved it to the redline at this point??? I then tried again, throttle off, a little throttle, but couldn't start it again..

In case I had flooded the engine, I turned the ignition off, fuel off, pushed choke down, open throttle fully, cranked the engine several times to clear it, then turned ignition no, fuel on, choke up etc...

I know the battery has nothing to do with it, although I think I should charge it anyway as the bike was SORN (it did come with a fresh day-old MOT) Surely the petrol can't be off? The seller started it fine, and it's only 3 weeks since he did it 2nd kick.

Am I maybe kicking too hard? I'm only used to the kickstart of the C50 so presumed this would need a hard kick.

Should I push gently until I feel resistance and then kick? Is it a good idea to try 2 kicks with the ignition off, choke down, and then ignition on, choke up?
If I get it starting, how hard should it need to be revved to stop it dying after 10 seconds? Surely it shouldn't need revving up to the redline to just keep it alive at this point?

Should I be twisting the throttle right at the end of the kick or does this just flood the engine for the next kick if that one fails?

Should it even need choke on a 10'C day?

One of the reasons I bought the RS was that I thought they were meant to be easy starters so it's most depressing to struggle like this.

Any pointers, help, even shaking of heads would be greatly appreciated.
Wilbur

[davebike]

Loud exhaust means the mixture will be way too rich at idle ! ( and probably too week at full chat ) This may well have blacked the plug ,

Don't start it and let it idle to much or you will need to clean the plug !

To get it going :-

Clean the plug or better replace it with an Iridium one!
NGK Dr8es-l is standard DR8eix the upgrade

Check the air filter (a foam rubber sleeve) is there and clean !

There is an interlink cable from the kick starter to the head for the decompresser c check this is free it may need adjusting but it is 15 years since I owned a CB250RSA and 10 years since I serviced one ! So I cannot remember how and I no longer have a manual !!

I would pull the float bole drain screw Philips/straight head at very bottom of carb

Form what I remember a good solid swing with little throttle got mine going it seldom needing choke
I don't remember it being particularly hard or easy to start just another bloody kick start bike !
OK not a fan of kick starts on bikes over 125 cc

[digger06]

if he has told you to check for compression, is the de comp cable still on?

a loud exhaust wont matter to idle much, dont worry about mixture,it could well be ok,cos the old owner could start it, so its prob new bike syndrome.. a good kick matters though,
feel for compression, get it just over ,lever back at top, then a GOOD FIRM kick, all the way , is the thing,

if its got a decompressor, it shouldnt matter, but i found getting rid and starting the old fashioned way the best,
iv had several honda singles, flood it, walk away for 10 mins, dont keep trying

[Wilburtron]

Thanks guys, that's some good stuff to work with.

I'm currently in a bedsit and the bike in a push bike shelter so have pretty minimal stuff, and my brother's sending me some of my tools tomorrow,

will check battery first - I'd forgotten being so used to points and kick that it's CDI and kick and the neutral light was a bit weak, also all the cables, for spark, colour of plug, drain the carb, check fuel lines, need to wait on ebay for the service manual about adjusting the decompression cable,

will be changing the exhaust in the future, way too close to other people's windows at the moment.

Thanks for the kicking/choke advice too - sounds more gentle than I've started to expect.

Cheers

Wilbur

[Wilburtron]

Argh, can't modify my post, please ignore the bit about battery not being important, of course it is,

[radar]

I owned and restored one these and my son has the CB250rs deluxe model.
Firstly the decompressor cable which is an adjustable cable, is there to open the exhaust valves a little to allow easier cranking/starting of the engine.In practice I found this of little use and kicking over the engine will require a bit of leg muscle. If you do a search on the internet you will find these bikes are a bit temperamental in the cold and you may need to play around with the choke in cold weather. the best thing to do is give the carb a good clean first. As regards noise these are single cylinder Thumpers and are loud particularly if you have a Motad exhaust, I personaly love the sound of them but you have your neighbours to consider.
They are great bikes

[Wilburtron]

Ahh, Is the Motad 2-1 loud? Below is the custom one, which is pretty loud but where I've got it is like a 3 sided amphitheatre so it really collects the sound too.

I was thinking that the Motad would be quieter and was interesting in switching them but if it'll be basically the same no point. Although I do want to re-extend the seat and get the pillion back on, it has been chopped a bit at the back btw.

[Dogsbody]

A Motad will not be louder than the original unless it has been altered. Exhausts are critical in length, volume and baffling, Honda will spend a lot of time and money with dynos and computers to make an exhaust system that will not only meet noise regs but flow the gases,create back pressure etc to make power in as smooth a way as possible. It is no use making lots of power if there is a great big hole in the midrange (talking road use here,not racing). I have seen so called race systems on the dyno, making enough noise to make your ears bleed, and producing less power than the original quiet road system. If you think some bloke in a shed with no dyno, sound analyser or R&D dept can make a system work , think again. It took 3 months work on the dyno to get a system for the VFR750 to make the same power as the factory system with no more noise to work. Dogsbody

[radar]

Here a short video of my cb250rs with Motad. might be a bit quieter than that beast of a Can you got on your bike
but they are loud when you open up the throttle

[Jon]

Starting a single is all about technique.

If it's cold, full choke.

If it's nbeen sitting for a while, look for the drain screw below the carb float bowl and with the fuel tank tap on let the old petrol in the float bowl run through for 20-30 seconds

Basically, you neede to press on the kickstarter until you feel the resistance of compression...Then, Continuing to press, very carefully allow it to reach the point where compression resistance suddenly stops. This means the piston is now at the top of the compression stroke and the only way is down...

Now...

Take you foot off the kick lever and let it return to the top.

Now, put your foot on the lever, lift your body up with your other leg and fall down onto and simultaneously push the kick starter in a LONG SMOOTH POWERFUL stroke.

If it doesn't go after 4 or five you'll need to leave it for half an hour.

Or...Choke off, and a few big full on kicks as described with the throttle wide open...Once it 'pops' you can go for a restart

The problem with Hondas is that they don't usually have decompressor levers and with one of those you can 'clear' the cylinder (ignition on, decomp lever pulled, wide open throttle, ten kicks through or until it 'chuffs' ...lights the fuel in the cylinder)

Sounds like a nightmare but after a while you'll be re-starting easily

Jon who had two SR500's and a Husqvarna 350 Enduro and was the 'go to' guy to start every other buggers big four stroke single dirt bike......600cc B50 based 12:1 comp CCM...yup...!!!