picked up an nc30 track bike for £300 from a gumtree ad last night. reckon i got a bargain buy has a penske shock and forks overhauled by reactive suspension a race exhuast system unknown make to me also came with a load of spares inc 2 spare wheels tyres 2 wheels with wets spare track bodykit and loads of bits n bobs in boxes including loads of those lovely little honda packs of components that will take me a week to go through fella i bought bike from said it was running well then developed a popping sound he did a bit of mild exploratory investigation lifted cam covers to check valves all ok, plugs out compression test ok then parked it up as he had bought a 636 kawa track bike .

he suspects the problem is possibly carb related perished rubbers air leak ? or could it be ignition related ?
its my intention to strip and rebuild the bike but will get it up and running first and see if i can get a clue to running problem prior to stripdown . any ideas of what i should be looking for or areas to check

I woudl check the valve clearences first, and perhaps you have a dodgy spark plug thats causing a backfire because of not firing all the time and allowing fuel into the exhaust.

skinnydog0_0 wrote:I woudl check the valve clearences first, and perhaps you have a dodgy spark plug thats causing a backfire because of not firing all the time and allowing fuel into the exhaust.

got a spare set of plugs will stick them in first before getting it running was gonna do clearances once motor out frame as a matter of course anyway from way he described it was under load and not overun just wonder if charging system meltdown may also cause this also

Could just be an airleak in the exhuast.

its a jap system unsure what tho has a plate on can jmic or something like that but think thats just a certifacation plate it looks intact unless maybe a port gasket has gone or its lmaybe leaking. fella said it just appeared after a session will get it going first and look for leaks .

ok think i have found the cause of the problem . was prepping bike for starting it oil water etc and cranked it over with kill switch in off position to get some oil on top end and could hear the popping noise the carb stub on the front left was sitting on the edge of the rubber not seated correctlly on further examination that and the r/h rear clamp was loose . removed carbs for now and have taken cammos advice on his excellent carb guide and ordered 4 new rubbers from david silvers before going any further and save myself a lot of strife getting them back on.

air box has no filter just the mesh fitted and snorkel and flap are present also discovered an hrc ign module cable tied onto the ecu and it has er10 plugs fitted ? on a further issue previous owner ran cooling system on just water for track regs i take it noticed top rad at filler is kinda brown and scaley so would imagine rest water pump etc will be likewise . i intend to use pro-cool in system and want to flush system prior to reffiling are the over the counter flushes that halfords etc sell ok to use or would i be safer just flushing with clean water several times first ?

davethetrucker wrote:ok think i have found the cause of the problem . was prepping bike for starting it oil water etc and cranked it over with kill switch in off position to get some oil on top end and could hear the popping noise the carb stub on the front left was sitting on the edge of the rubber not seated correctlly on further examination that and the r/h rear clamp was loose . removed carbs for now and have taken cammos advice on his excellent carb guide and ordered 4 new rubbers from david silvers before going any further and save myself a lot of strife getting them back on.

air box has no filter just the mesh fitted and snorkel and flap are present also discovered an hrc ign module cable tied onto the ecu and it has er10 plugs fitted ? on a further issue previous owner ran cooling system on just water for track regs i take it noticed top rad at filler is kinda brown and scaley so would imagine rest water pump etc will be likewise . i intend to use pro-cool in system and want to flush system prior to reffiling are the over the counter flushes that halfords etc sell ok to use or would i be safer just flushing with clean water several times first ?

What jets are in it? It is going to be a ballache, I can feel it in the force!!

ER10s are also a pain, if you tink killing ER9s is easy...wait til this won't fire and kills them!!

CMSMJ1 wrote:

davethetrucker wrote:ok think i have found the cause of the problem . was prepping bike for starting it oil water etc and cranked it over with kill switch in off position to get some oil on top end and could hear the popping noise the carb stub on the front left was sitting on the edge of the rubber not seated correctlly on further examination that and the r/h rear clamp was loose . removed carbs for now and have taken cammos advice on his excellent carb guide and ordered 4 new rubbers from david silvers before going any further and save myself a lot of strife getting them back on.

air box has no filter just the mesh fitted and snorkel and flap are present also discovered an hrc ign module cable tied onto the ecu and it has er10 plugs fitted ? on a further issue previous owner ran cooling system on just water for track regs i take it noticed top rad at filler is kinda brown and scaley so would imagine rest water pump etc will be likewise . i intend to use pro-cool in system and want to flush system prior to reffiling are the over the counter flushes that halfords etc sell ok to use or would i be safer just flushing with clean water several times first ?

What jets are in it? It is going to be a ballache, I can feel it in the force!!

ER10s are also a pain, if you tink killing ER9s is easy...wait til this won't fire and kills them!!

I'd put a standard air filter back in it also if its running standard ish jets, as Mark will tell you ive just had a nightmare with mine and by the looks of it it was aftermarket air filter related.

advice taken on board guys thanks, must admit unfiltered is not really something i would consider doing but its been used as such so retro fitting one may be a bit late can see a bit of mild scoring on slides as a result of this and theres most likely worse inside . trying to fit in time on it when i can because of work my main intention is strip it and rebuild it as a track bike later, but want to get it running first . got some 9s spare will put them in and as the carbs are off have a look inside too whilst awaiting new carb rubbers.

i have a spare engine which needs just a manifold and water pump so might use that if this ones fubar.

I would suggest seeing how it runs first before deciding on what air filter route to go down - my money is on it running like an absolute pig. Take the previous owner's comments with a grain of salt, he did offload it cheap...

If it does run badly a standard air filter is the best way forward I reckon.

Good idea to see what's inside the carbs, make sure to write everything down for each carb (main jets, pilots, needles & washers etc) so you can always compare this to how it runs.

With a little sorting it sounds like you've scored a bargain mate!