Carbs rejetted now wont start

[85Coupe]

Hi All,

please can someone help me?

I recently aquired a NC30 that ran really well except it hit a flat sopt at 10500rpm and then had no more power and would seem as though it was limited after that.

I took the carbs apart and found 115 and 116 in the rear jets and 115 and 114 in the front. the emulsion tubes were also mixed up with the 4 holes in the rear and 5 holes in front. I corrected the emulsion tube locations, cleaned the carbs and closed them up with new gasket sealent with 120front and 122rear main jets (bike has aftermarket end can and is quite loud compared to my std NC30)

I put it all back together and then took her for a spin, the flat spot was gone but she would not rev right, took very long to move up in the rev range and was down on power. I assumed it was running too rich. It almost sounded like it had an exhaust leak...

So, stripped carbs again and replaced with 118f/120r. At the same time I saw some (what looked like) carbon build up in the intake manifold going into the combsution chambers around the valves, so I sprayed a healthy dose of carb cleaner into the cylinders whilst the carbs were off which with hindsight was a dumb idea.

Now I have re-assembled the bike and she wont start at all, I got a backfire and a flame or 2 out the exhaust but no joy.

Have I now ruined the plugs by getting them wet with the carb cleaner and perhaps flooded the motor with numerous attempts to start, I did use some throttle to try and get it going? How do you 'unflood' the bike? remove carbs and drain?

I am new to bikes so some advice will really help. I am not totally clueless mechanically as I have built my BMW E30 from the ground up alone using the web and haynes manuals.

P.s. the carb rubbers make a good seal, I checked for airleaks and there are none. Lastly, it seems there is fuel going to carbs, as if I pinch the fuel like to the carbs when starting I feel the fuel pulse by in the pipe.

thanks guys.

[85Coupe]

Hello,

I forgot to mention, I also added 2 x 0.5mm washers on the needles as there were none on when I checked.

[dobbslc]

Mmm gasket sealant, that stuff will probably have dissolved in neat fuel.
It then gets into the smallest jets & drillings ie the starter circuit and causes all kinds of problems.
Also did you touch the pilot air screws?
They should be a turn and a half or so out from fully in. Someone here will know the correct settings.
In the past those small Honda plugs seem to be really easy to foul up so maybe a new set of plugs will help.

[85Coupe]

Hey Dobbslc,

Thanks for the reply. I used Victor Reinz gasket goo, so it is very resistant to fuel. But that is a thought.

I did the carb rejet as per Cammo's write up and there was no mention (as far as i saw) of the pilot jet screw, it basically just said, remove, clean, replace. This is what i did.

Does the pilot jet merely control idle? As my idle is perfect, its when the bike is under load that all the problem comes in.

thanks!

Please keep the advice coming.

i will try and swop the plugs out tonight with my project bike as it runs fine.

regards,

[tigerclaw]

Hay man, those jets are to big in JHB 110 jets is what you need (I have 110 with a maggot exhaust). Also if it is backfiring check you havent mixed up the firing order (plugged the wrong coil onto the wrong sparkplug)... could also just be to much fuel in the exhaust busy catching fire.

If you dont come right take it to Racebox in Edenvale, they now VFR's really well and they are a nice bunch of guys

[Cammo]

Flooded - always is.

New plugs will fix it but you might get lucky by taking yours out and drying them over a flame.

[hunter]

Flooded - always is.

New plugs will fix it but you might get lucky by taking yours out and drying them over a flame.

[85Coupe]

Thanks guys, @ Tigerclaw, i will try 110 jets, but why would i have the 10500 flat spot?

Is that not a sign of underfuelling?

Would you suggest 110 jets plus raised needles then?

Replaced plugs and started up but now idle sits at 6k? And alot of vibration throughout rev range.

Thanks again.

[dobbslc]

Vibration could mean it's missing on one cylinder,
A high idle means an air leak are the carbs back on properly? They can be bitch to seat well, or maybe a throttle cable being snagged.

[tigerclaw]

I am not sure. If the bike is slower than usual to rev then I think you may not be on all cylinders. Otherwise I think the guys may be right about an air leak. But no jokes speak to gerhard at racebox he will know and he usually had spares if you need