500 wont start

Jeremy Wilton

Jeremy Wilton

Junior member
Location
Cropredy
Here we go: Newly built bike - filled the tank with about a pint of juice from the lawn mower can - ran fine after a turnover or two. Left it overnight, went to get the MOT - started with choke - but forgot to turn it off. Went about half a mile - engine revving. Couldn't get to the knob under the tank - Stopped at side of road and turned choke off. Engine started, but getting boggy. I thought it was short of fuel. Stopped and got a fiver's worth of juice at the Fina garage... Then she wouldn't start... engine bogged and leaking left hand carb.
Two days later having pushed the bike home - still no start. Good spark on each plug, but when I pull them from the head they are soaked in petrol - plus a little oil... Have changed the float height 15 times, but no sign of any difference... still floods a little from the left, but how come both plugs are soaking?
Could it be ropey petrol - surely it would start a bit... shall I replace the Dell Ortos carbs or just the needle valve (only 250s available - not 265s?)
Quite pissed off! But won't give up!
 
Take the tank off and check that the choke plungers are returning and not jammed in that shit lever set up, if you have fuel leaking from the carb either side take the float chamber of and with the petrol tap turned on gently push the float up and check if the float valve is actually stopping the fuel flow if not there is an issue with the float valve or needle and seat maybe the seat is not tight against the fibre washer that sits under it???
If you manage to identify the problem fit a new pair of plugs and get the engine to start shut the choke off as soon as possible ensuring the choke plungers close.
 
I would initially focus on the chokes as you mentioned leaving them on, and then the issues started.
Why would the jets be the problem, as there is excess fuel on the plugs.
 
Always best to change out the float valve assemblies on a carb rebuild. Dave's prices are the keenest around, although he's a scooter man the 5mm and 6mm jests and some other parts are common to the PHF's.

https://www.wasp-performance.co.uk/onlineshop/prod_4028992-Carburettor-Float-Needle-Valve-250.html

Good luck,

Ian
 
Hi Jeremy, if you get stuck, I have the refurbished standard carbs off  the road bike I used as a donor, I had them professionally cleaned and replaced the jets and needles then decided to go for two brand new Keihin carbs

Dont know what they are worth but I am sure people will suggest a reasonable price, it cost me ?45 for the cleaning then about the same for jets etc, I also have a couple of larger main jets that I bought for when I took it to the dyno

This is the before and after pics, it may save you having to chase around but dont worry if you ant to stick with your originals that you already know - I get that, the only thing that was not changed was the throttle slides
 

Attachments

  • Lav carbs.jpg
    Lav carbs.jpg
    17.8 KB · Views: 27
Cheers Fitz - may take you up on that (have got float valves ordered anyhow from Laverdaton's suggestion) I think you know the bike I am working on it came from Terry in County Durham...
 
You must log in or register to reply here.
Back
Top