NC30 track bike not been used in 8-10yrs, where to start?

[Cammo]

The throttle butterfly sort of covers the holes when in its resting position. If you move the butterfly out of the way slightly you'll see the leading side of the butterfly shrouds these holes.

They're difficult to see unless you have good lighting.

The symptoms do sound like blocked carb passages are responsible.

[28hodge]

Didnt get round to doing anythingthis weekend, got sidetracked and felt pretty rubbish on Sunday so just pulled took the carbs home and took the float bowls off to replace the pilto jets and also bought a set of allen screws from Rick for the carbs, as all my screws show signs of years of abouse.

Looked at the butterfly holes and will give them a good going at with the compressor and carb cleaner, fit the new rubbers and full airbox combo and give her another run.

Im off tomo friday so got a good 4 days run at it so hoping to get some of the following done.

Brakes bled up and fully working
Carbs re fit fettled and all four cylinders firing
Finish arranging my chopped down subframe
Sort undertray out and fit to subframe
remove rear shock in preparation of fitting rs250 shock.

If i can just get it running and idling right i'll be happy to be honest!

[28hodge]

Didnt get as much done as i wanted yesterday as the elec was off from 9 till 3 which was a bit of a ballache, as was trying to fit the new carbs rubbers and carbs using a headtorch, but i managed.

Had the carbs off to fit rick's carb screw kit as all the heads on my carb bolts were buggered to be honest, put new pilot jets in all ths carbs. also had a good look at the pilot circuits and the 3 holes round the butterfly and gave them another scrub and blast of carb cleaner, re fit them and then started it up, and it ran on all 4 cylinders beautilly, for about 30 secs and idled bang on 1.5k, then it dropped back onto 3 and ran up to 4.5k.

The new pilots has got the front right cylinder up and firing and the front left cylinder chugs away, the pipe gets warm but not hot, unless you rev it then it comes hot as if the pilot circuit isnt still fully working but when it comes onto the main it starts to fire and run.

Still running fast tho, no leak on the carbs as sprayed easy start round them when running and no change in revs at all, but i havent refit the airbox as it hasnt got a filter so waiting for one to turn up, would this be enough to allow the bike to idle 3k quicker than it should? if i choke the intakes a bit, ie put my hand over them and restrict their airflow the revs drop off and the bike runs a lot nicer.

Next problem is the bike is and has been a trackbike for a lot of years and has the hrc tap mod, fine i always turn my fuel off as its a habit from racing motocross bikes for the last 20 odd years, however lifted the tank off yest with the tap in the off position, and its leaking fuel, fiddled around with it opening and closing it and it seems a bit hit miss or maybe. sometimes it shuts and seals and so doesnt leak and other times it leaks.

Quick panic so dipped the oil and sure enough i think i smells of petrol, and seems pretty runny. however my floats all appear to be working so really fuel shouldn't be able to get through the carbs to the bores and past the rings should it?

Got some fresh oil this morn and will take the old out and use it for chain lube on the mx bike through winter.

Best option for the tap i guess is a dry break yeah? is the fuel pipe 6 or 8mm tho? or if i get a tap kit from rick and then do the hrc mod to it will that solve the leak?, i suppose the best option is actually doing both of the above.

Anyway back out today, gonna have to have a look at refitting the exhaust as its sounding a bit tractor like think its blowing on the rear manifolds as they were a complete bitch to fit, not overly happy with the fit either to be truthful so was going to take it off again anyway.

[28hodge]

Been off work since the 21st and although not had the time I really wanted I have been able to get some things done and progress is definately being made.

Removed the entire read end of the bike and shock to get into the exhaust to fit it properly, got the headers on to the cylinders and the. Started fitting the mid pipes, what a complete pain in the bum of a job this was, got a full micron system with the. Joe when I bought it but it's never been fit onto this nc before, it has been fit to something as it has a ding and scrap on it. It rubs a little on the rear shock and the 4 into 1 manifold took me over an hour to fit also bit worried the chain may slap the pipe!!! Not really sure what to do about that!!

Sorted the front brakes all bled up and got a real good solid lever which im happy with, fitted the front mudguard which was trickier than I expected!!

Still can't get it to run 100% tho, full air box on it now and no air leaks what so ever, can spray easy start at it all day long and no change in revs, runs on all for so pilot circuits all cleaned out but it still idles at 4 - 5 k!!! Pilot screws are 2.25 out, starting to run short on ideas a little now really!

Should the slides be bottomed in the carbs? If not how high should they sit, mine do not sit to the bottom.

Also the bike backfires quite alot, more than I'd expected used the 4stroke m. Bikes but they don't spit flame too much!!

Anyway also mocked up my race subframe from timber and will try to construct it from ally tomo, tho not holding my breath, my dads mate is a fabricator so he may be getting a call!

Also need a rear brake as mine is beyond salvaging, the pins stuck and the pistons are stuck right in and not for moving even with compressed air.

I'll put some pics up tomo as I'm on my phone at the minute

Any further pointers on the idling be good

Thanks
Kurt

[Neosophist]

slides should be fully seated.

Have you unscrewed the idle adjuster fully?

Are the throttle cables sticking.

Another one is the 3 balance screws.. if somebody screws them in too much they won't let the butterflys close fully and keep a low idle.

These engines when properly setup idle as smooth and steady as any modern fuel injected bike i've seen. (can provide videos if you want!)

[28hodge]

Throttle cables are good, idle adjuster is fully out and not touching the throttle pulley, I'm gonna pull the carbs off and make sure the pilot screw adjusters have their washers in them still, the butterfly's look fully shut. It as the carbs are coming off I will double check the 3 adjuster screws, keep plugging away and it'll run bang on eventually.

Thanks for the pointers
Kurt

[Neosophist]

Throttle cables are good, idle adjuster is fully out and not touching the throttle pulley, I'm gonna pull the carbs off and make sure the pilot screw adjusters have their washers in them still, the butterfly's look fully shut. It as the carbs are coming off I will double check the 3 adjuster screws, keep plugging away and it'll run bang on eventually.

Thanks for the pointers
Kurt

Have you checked the choke rods too? if you remove the caps and diaphram / sliders you can see the choke mechanism.. it's possible to adjust the choke rods so that even with the choke cable turned off they are still engaging slightly... (the rods are on screw adjusters)

Might be worth checking whiel you have the carbs off

[28hodge]

Thank god for that, sorted and idling at 1.5k and not bouncing around the rev range just sat bang on 1.5k so happy about this, slightly concerned that its not running on all 4 at idle tho, so guessing the pilot circuit isn't complete ungummed as all four come on song when you rev it up.

The problem was two of the butterflies were not completely shut but just slightly cracked open. I removed the carbs and shined a torch through from the engine side of the carbs, two seeped light through pat the slides, two didn't so I've adjusted those two so the butterflies are completely shut, refitted the carbs and it ran so much slower, so happy it's running alot better.

Having said that it did piss fuel outta the carb vent/overflow pipe, never done that before seems strange as not touched the floats.

Forgot my laptop today so will post some pics up tomorrow.

Thanks for the pointers
Kurt

[royster81]

I might be wrong but I thought the idle adjuster had to be screwed in and touching the throttle drum to correctly balance the front left cylinder, and if it wasn't that cylinder would be closed tight.

It would idle on 3 and when you opened the throttle it would open the butterfly and the forth would start working.

[Neosophist]

I think your adjustment screws might still be too tight.. did you back them off to close the throttles?

My bike will idle down to as low as around 700rpm when warm, if you turn the throttle adjuster anymore out it dies, but it still runs on all 4.

You either have the blocked pilot circuit (it's those 3 small holes by the butterly) (high compressed air and carb cleaner is good here) or somethings not quite right.

When did the excess fuel come out?