El Gringo Posted March 1, 2012 Report Share Posted March 1, 2012 Hi All, Just a bit of a pre inspection question really, i've got an NC35 to have a look at, it has been stood for a little while and prior to this has experienced some running issues. Starts fine on choke and when it warms up will tick over quite happily. Problem is when you rev it up it bogs down and unless you are very gentle with the throttle opening it won't rev past 5000rpm. Crack the throttle and it bogs to nothing until it nearly dies then if you back off stutters its way back to idle again. I've done a bit of research and the 5000rpm thing could be the 180kph speedo restrictor cutting in early (due to lack of 12v feed to the CDI) but i've no idea why this should be as it ran fine for years. As i say i haven't had a look yet but if any of the NC30/35 gurus have any initial thoughts it would be much appreciated Ta Chris Link to comment Share on other sites More sharing options...
stuntmonkee Posted March 1, 2012 Report Share Posted March 1, 2012 Clean the carbs, change the plugs... Link to comment Share on other sites More sharing options...
nigel.ted Posted March 1, 2012 Report Share Posted March 1, 2012 Air filter clogged, had the same problem on my RF900 worth a try, mine had been stood a while as well, would start and run fine but would not rev over 7 k If it black smokes when you shut the throttle thats it. Link to comment Share on other sites More sharing options...
lorenzo Posted March 1, 2012 Report Share Posted March 1, 2012 They're really sensitive to plugs. Link to comment Share on other sites More sharing options...
CMSMJ1 Posted March 1, 2012 Report Share Posted March 1, 2012 They don't want to rev in neutral. the 5.5k revs thing>>if the CDI cannot see the speedo then the 2 rear sparks are cut. it can rev higher than 5.5 but sounds nasty and harsh. If it has been sat, then you are looking at some carb cleaning and a good fettle. Link to comment Share on other sites More sharing options...
El Gringo Posted March 4, 2012 Author Report Share Posted March 4, 2012 Minor update. Plugs out, not too bad could do with replacing, Air filter - black as a coal miners hat, needs replacing but got a blow out and clean. Drained float bowls and tank - no water The it got worse, 3k bogging followed by no revs at all. Had a blow down the vacuum tube, ah whats this then? Yep it came off in my hand, split right at the stub. One quick pipe replacement later and we're pretty much sorted. Still takes a long time warming up before it will rev cleanly but rev it did right through to the redline. I think it just needs a good thrash to clear it's pipes Still has a bit of a cough at 5.5-6k but again it needs running properly before i can call it. Also it's on a second set of carbs and none of the jets were swapped over from the original set (not that i think they were set up in the first place) and it's got an MHP twinstack half system which might be causing the dip. Also the reg/rec decided to throw the towel in and the connector melted and burst into flames which probably won't be helping! Biggest problem is the owner hasn't got/doesn't want to spend any cash on it really. Thanks for all the suggestions, will keep you updated. Cheers Chris Link to comment Share on other sites More sharing options...
drunkn munky Posted March 4, 2012 Report Share Posted March 4, 2012 No NC will rev cleanly until warm. He really should put his hand in his pocket and buy new plugs and filter, it'll make all the difference. That and a bit of TLC on the carbs should see it right. Link to comment Share on other sites More sharing options...
El Gringo Posted March 5, 2012 Author Report Share Posted March 5, 2012 Another update, having thought it was sorted yesterday, came back to it today and got the same bogging at 5k. Having thought about it a bit, i swapped the carbs back to the old set that were supposedly the cause in the first place, and after a thorught clean i got the same result. Whilst deciding on the next course of action i stuck the battery on charge and went to have some lunch. Came back an hour or so later, flicked the switch, much smoother idle on choke, 3-4 minutes warming and zing!!!! straight round past 5k no blip at 6k, nice and smooth. Now i'm thinking it was the rectifer all along, with no charge going to the battery, it was getting a weak spark under load and cracking the throttle was effectively snuffinf out the ignition. Would also explain why it ran better when it warmed up, as i'm guessing it wouldn't have to spark as hard for an ignition with a fully warm cylinder. Does that make sense or am i talking bollocks? New rectifier is on it's way so we shall see. Cheers Chris Link to comment Share on other sites More sharing options...
El Gringo Posted March 7, 2012 Author Report Share Posted March 7, 2012 New Reg/Rec on and it's running sweet as, charging at 14.5 Volts and not a cough or splutter at all. Result. Thanks for all the responses. Cheers Chris Link to comment Share on other sites More sharing options...
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