[New member with a headache of an xs250]

Finally got chance to spend some time on the bike and managed to get it running numerous times for about 20-30s before cutting out. 
 

To do this I cleaned the carbs fully again and then tweaked the air/fuel mixture screw and the timing very slightly until it started going. 
 

When I put the H pipe and filters on it made it worse even when I tweaked the mixture screw. I’ll keep messing and see if I can get it to run for longer. It also wouldn’t Rev but I’m guessing that’s due to having no filters on? 

 

 

[New member with a headache of an xs250]

Thanks, 

 

Iv give the carbs another full clean today, found a bit of wear on one of the slides and the slides seem to be sticking so not sure if that’s linked. I’ll pop them back on and see if it makes any difference. 

[New member with a headache of an xs250]

1 hour ago, drewpy said:

pods on the (Y?, shouldn't that be H?) lineate the air flow for the CV carbs  

Sorry yes that should be a H. 
 

So as long as I’m using the H pipe I should be ok? 

[New member with a headache of an xs250]

I’ll double check on the plugs then work back from there and let you know how I get on.

im running from a auxiliary fuel tank as the bikes tank needs sealing. 

 

thanks for the help. 

[New member with a headache of an xs250]

Thanks for the advice,

 

I was struggling to get the points set up as Iv never done it before which is why I went to the newtronics as it looked a little easier to setup. I’ll dig out the points and see about maybe putting that setup back on. 

I did have another look over the timing again and I’m pretty confident it is right and almost got it going. I put some fuel directly in the cylinders and with the throttle wide open it was very very close to starting but still no luck. This made me think that maybe the carbs arnt getting any fuel to to cylinders so will give them a full strip down clean and double check everything is set up correctly again. 
 

One thing I forgot to mention earlier that maybe quiet important is the guy I bought it off had it running on pod filters on the Y pipe from the carbs. I have put new standard jets in and wondered if this maybe also causing issues if he had jetted the carbs to suit the pod filters? Am I fighting a loosing battle trying to run pod filters on these carbs? 
 

thanks for the advice so far it’s got me closer than I have previously to getting the bike going. 

[New member with a headache of an xs250]

15 hours ago, drewpy said:

they are simple machine, i assume you have the soho version?

check your timing as you can be out 180'

have you touched the engine? did it run before?

carbs are a big issue as there are some tiny drillings in there and they need a proper ultrasonic clean. you can check by spraying easy start to see if you get a sniff from the engine

Hi Drewpy,

 

Yes mine is the SOHC, It was running (on points) when I got it but can’t get it back running now since putting back in the frame after powdercoating. 
 

I have done the following:

Newtronics Electric ignition (condenser removed) 

Carb clean (ultrasonic) and rebuild with new jets, mixture screws and diaphragms. I have also cleaned again since trying to start. 

New battery

New coils.

New HT leads.

New plugs.

Valve clearances checked.

Timing check several times. (Followed the instructions but was back firing through the carb on one cylinder so timed 180 out to the instructions which stopped the carb bike fire and large backfires through the exhaust but still not starting.)

Good spark from both plugs.

Compression using thumb over hole seems ok but need to check properly with a guage.

 

Think that is it, quite a few changes which doesn’t help narrow things down.

I have tried easy start through the carbs and it changed nothing. Next plan was to remove carbs and try a small amount of fuel in the cylinders and see if that helps. My thought is if it goes like this then the carbs are the issues? 

 

it’s all new to me and a steep learning curve as Iv only ever messed about with cars and nothing this old so if any of the above is wrong or a bad idea then any advice would be appreciated. 
 

I really don’t want to give up on the last hurdle and take it to a workshop after doing all the other work myself. 
 

Thanks

 

 

[New member with a headache of an xs250]

Hi all,

Currently in the later stages of my first build, turning an XS250 into a street tracker.

Hoping all the knowledge on here will help me get the thing running after scratching my head for the last month as to why it won’t start. 
 

Thanks 

Paul