xbr5 not revving and cutting out over 4000rpm

[andyha93]

Hi,I have been putting a donated xbr back on the road and I love it,taxed insured and passed mot but started to splutter over 4000rpm coming back from mot,thought it was fuel starvation,stripped carb again and checked float hight(non adjustable,thanks honda) but within tolerances,plug showed was running lean so lifted needle by 0.5mm(needle non adjustable)with tiny stainless washer,made problem worse and plug getting hot and starting to whisker.The carb flows fuel well with drain scew removed,tank breather fine and choke cable carb body screw arraldited into carb so no air getting in there and the vacuum rubber is well sealed as are the inlet rubber and strange bakelite mounting plate.seems to rev ok when not under load but at am a loss....Please help or pray for divine inspiration.I live in Ulverston in the south lakes and my local train line closes for 4 months for viaduct repairs tomorrow.I am trying to buy a new carb to stick on if anyone has one and if that is'nt the problem will start grumbling and start on the electrics.Any ideas greatly welcome.   my phone 0750 4179875...e.mail ahahorsley@gmail.com. cheers Andyh

[blew]

When I bought my XBR it had a top speed of 70,and was reluctant to rev..After trying everything else,I eventually lifted the rocker box and found the cam timing was one tooth out.

[pigafetta]

Hi AndyH

Are you using standard air filter/jets (main 152, slow 48 according to my manual)? When you stripped the carb did you blow it all through with compressed air? Is the o-ring on the pilot screw missing/knackered? Is the air cut-off valve in good order? Diaphragms all ok?

I'm just trying to think of things, It sounds like a main jet issue to me.

Dave B

[andyha93]

Thanks for your replies and suggestions.Got a 'new to me' carb coming from john in Derbyshire,cheaper option than buying bits n pieces.If that don't fettle it I will be having a short calming holiday before starting on the electrics.

[SteveC#222]

Sounds like a good move. Remember to hang onto the old carb for future spares - a new diaphram is £100!!