Misc: Everything Else Starts, runs then slowly "chokes up"

[doctired]

Hi, my 48 Rap starts well and runs fine for about 20 miles before it begins to struggle and has to be coaxed home with a stumbling, dying at low revs engine.. any ideas?
Full rebuild by Maughans before return to road 12 months ago. Series D ignition and Alton. Grosset starter. Monobloc carbs and conical Amal filters...
All clean and sweet...
Any Ideas gentlemen?

 

[Robert Watson]

Breather hole in the fuel cap plugged??

Been there done that.........

 

[doctired]

Thanks for your kind help. I did look at it but it seemed ok. Is there a top quality replacement or a repair anyone may suggest as a first line?

 

[Robert Watson]

When you are riding along and it starts stumbling, open the fuel cap - that's a sure test!

Do you have fuel filters? If so they could be at issue.

Certainly sounds like fuel starvation.

 

[doctired]

Will give it a try. No in line filters. Will get back in a few weeks. Had kickstart leg hip replaced 2 weeks ago. Electric start on Rap as you can see...new one ready for fitting to my 54 Shadder...
Very grateful for input and advice. Kind regards J

 

[chankly bore]

What do the plugs look like? Also, some Monoblocs are machined not to have a fibre washer below the tickler assembly.

 

[doctired]

Thanks. Will check tomorrow am. Grateful for your help...

 

[Robert Watson]

What do the plugs look like? Also, some Monoblocs are machined not to have a fibre washer below the tickler assembly.

But wouldn't that only make the tickler a little short if the fibre washer was put in?? I don' think a tickler problem is what is causing the engine to stumble 20 miles down the road....

 

[Bill Thomas]

How about the filters on the petrol taps ?, Has the Tank been treated ?.
Take the pipe off at the tap, And see how good the flow is, And for how long ?.
Good Luck, Bill.

 

[chankly bore]

But wouldn't that only make the tickler a little short if the fibre washer was put in?? I don' think a tickler problem is what is causing the engine to stumble 20 miles down the road....

Yeah, correct Robert but I'm trying to narrow down whether it is too much fuel or too little. I worked on a Panther that had just this problem with a Monobloc. My first question is always about plugs because they can tell you a lot, quickly. Anyway, as I always say, I read too much poetry to be useful. Put a bit of gaffer tape over the fuel cap vent and run a 3/32" drill through the breather hole, then remove tape. Also check the underside hole on the brass "dish". Cheers.