2 stroke warm start problems

[Gingermick]

My flamin bloody motorbike doesn't like to start when it's warm and I can't find a reasonable answer online.
Was wondering if anyone could help?
Thanks

[wheelinround]

Airo-Start if your desperate but beware you'll need to rebuild the engine after a few uses

GingerMick is it 2 stroke or 4
Is it a honda

[Gingermick]

Well that's not much use. some bloke on the road mentioned vapour troubles from a leak in the carby

[wheelinround]

Sorry Ginger its 2 stroke

If there is vapour leak a new Gasket may solve the problem even checking to see if carby is loose

[Gingermick]

RZ250, it's a classic

[wheelinround]

this the one

http://www.motorcyclespecs.co.za/model/yamaha/yamaha_rz250%2080.htm

Just found this

is that your quetion
http://www.classicmotorcycling.com.au/Forum/topic.asp?TOPIC_ID=1417

[Gingermick]

no, this one
http://www.strappe.com/rz250r.jpg
I don't have any issues with plugs oiling up and my injectors work fine.

[wheelinround]

Ginger check the fuel tank for water just a thought

[manoftalent]

sounds like its running too rich.....screw the fuel mix needle all the way in as far as it will go ...then turn it back 2 1/2 turns ...give or take a 1/4 turn it should be about right ....also pull the plugs and see if they are fouled ....might as well clean em and regap em while your at it ...I would probably dump all the fuel and refuel with a fresh and accurate supply should this fail......if this doesnt fix it then you have one of these problems

sticky/burnt valve ....worn carby gasket or dirty needle ...or the float level is screwed ..

good luck :doh:

[Ashore]

What brand and type of plugs are you using :?

[Gingermick]

NFI, but I do ride around with the revs up, to make sure the plugs don't gum up and also to make sure that if I need to go it goes:D sounds a bit like a water ski, but light and agile and would go even faster if I didn't weigh 105kg.
A bloke walking by me pushing and kicking the thing said it would be a carby gasket causing a vapour lock. or something like that
The problem is so infrequent that I couldn't be bothered taking it to the mechanic.

[wheelinround]

Ginger this is sounding more like a loose carby bolt/nut/stud caused when it gets hot it then sucks air throwing out the fuel air mix

Now you need to be careful DO NOT over tighten as you can literally pull the stud through the body of the cardy being light material Alli.

mate had similar on his think RD360/380 way back and the older road 250's did it as well
its a simple fix if it is that but best thing with it is a new gasket as well

If it progresses it can stall on you when you dont want it to ie: in a corner powering on, trying to pull out of the way of blind motorists :oo:

[Cliff Rogers]

90% of problems with 2 stroke motors are the plug.

Try a new plug.

I've even had a 4 stroke Honda motor that would not run once it was hot, it was the plug.

[Gingermick]

Serviced only a few weeks back, so plugs are quite new, and thanks wheelin, just gotta find the carby now, bloody farings look good but dont make for easy access:oo:
ta

[Ashore]

Mate plugs aint just plugs but the engine is designed for a particular plug , try for your model yammy try DENSO Hot U standard plugs, or better yet get a BMW , or even a Honda just not that 2 stroke rubbish :D:D:D:D

[Sturdee]

Serviced only a few weeks back,

Don't know anything about motorbikes but I had the same problem with a Ford Fairmont Ghia adapted to run on gas. Great on a cold start, but restarting within 20 mins of turning engine of was impossible.

Neither the RACV nor a ford dealer could find the fault, but talking to a home mechanic one day whilst walking in the street he suggested to increase the size of the cables from the battery to the starter motor and earth. Did this and never had any problems again.

So it may be in your cables and may be worth looking into if all else fails.

Peter.

[Gingermick]

Yes, I spoke the people who sold me the bike and they said that it sounds more like an electrical problem. Increased heat in the electrics ups the resistance in the cables so spark may not get through. I'll have to check that out
cheers peter

[Gingermick]

just not that 2 stroke rubbish :D:D:D:D

It uses less fuel than my previous bike ,a 4 stroke, 110cc honda.

[Ashore]

Increased heat in the electrics ups the resistance in the cables so spark may not get through.
also why you need the correct spark plug, btw is yours the 87 or the 88 model ?

[malb]

It uses less fuel than my previous bike ,a 4 stroke, 110cc honda.

Course it does, you're pushing it or looking at it, not riding it.

[Gingermick]

also why you need the correct spark plug, btw is yours the 87 or the 88 model ?

86


Course it does, you're pushing it or looking at it, not riding it.

Well you see I had to ride the postie bike pretty much full throttle all the time (it had trouble on the 100kph zone) and it used a lot of fuel that way.

[Ashore]

Anything pre 88 the DENSO Hot U standard plugs are the way to go though its still 2 stroke rubbish :D:D:D

[Dingo Dog]

Have you checked the coil. Back in the early seventies I had one of those TY250 Yammie Trials bike, while out the back of Mt Coota with a bunch of mates annoying the country folk with our bikes we stopped for a rest. I went to start the bike but it would not fire. pulled everything out there and then. Motor cold it fired up. Took a couple of days before finding out the coil had failed.

D D

[Dean]

Had similar issues with my 2-stroke outboard motor. Wouldn't start when hot. It could have been a few things but likely that the spark plug gap was too wide causing a poor spark that seemed exacerbated when the motor was warm... perhaps the gap widened ever so slightly when hot? Check the spark plug gaps are what they should be for your motor. Sometimes the plugs suggested for your motor don't have the correct gap out of the box and require re-gapping before putting them in and using them.

I ended up changing the ignition coils too :) This might also have been the cause so check that.

Also check fuel is getting to the motor. My outboard used a vacuum type fuel pump and after warming up then stopping and letting it sit for 5 mins it would lose its vacuum and require re-choking and several yanks on the start cord to get fuel flowing again.

So might be any of those too if they relate to your bike motor?

[Ivan in Oz]

Mate plugs aint just plugs but the engine is designed for a particular plug , try for your model yammy try DENSO Hot U standard plugs, or better yet get a BMW , or even a Honda just not that 2 stroke rubbish :D:D:D:D



Gingermick,

Have you done any Leak Tests for escaping Air abound the carb?

ALSO;

Would you mind telling Ashore what to do................:rolleyes:

I have just fixed an "ISSUE" with my Honda H100 2 Stroke
It had Water in the Gearbox and Diff oil.

Made some nice mayonaise:doh:

Normal bike is a Goose.........Guzzi for the Unknown

[Chris Parks]

Fixed it yet? Another issue may be the float bowl vents, you would be better off just rebuilding the carby, after you find it under the fairing that is. Floats sink, vents block up, gaskets leak, needle & seats dribble etc.