Got a GK76A SP, Just whacked new engine in, Standard pipe, Sandybikes Downpipes, SP carbs, Standard Airbox.
Air mixture screw 1.5 turns
Pilot 47.5
Mains 105
Needle clip in middle.

Has Litetek's Vitron seals into can't be seals. puffing black smoke about 8k+, wont idle for poo. Will idle about 3.5-4k and itll sit like that, move throttle abit then will got to 2k then die. Got a morgan colortune and carbtune, shows yellow about up to 5k then blueish after that :/ so confused rather. I had 50 pilots in before and it did idle and run a bit better but thats going rich again were by look at plugs and colortune its already running rich on 47.5's :/

Hi Mr Marsbar,
Regards the colortune it seems to be giving you false signals. The best way, IMHO, to set idle mixture is by ear.
The only experience I have with a colortune was a friend (mechanic) who bought one and it was basically useless. This may have been a faulty unit for all I know but if you are getting conflicting signals then I would be wary of relying on it completely.

If the idle will not settle it is usually because the pilot circuit is too lean. What is the standard number of turns out for the pilot screws?

As for high rpm. If you have a fresh engine it will probably need less fuel than before. How about the mains jets? The parts book I have shows them as #100
Float levels and diaphragms ok?
cheers
Blair

Hey, Thanks for your response.
I can understand that the color tune could give false readings possibly because it is not the correct spark plug, just a thick bend wire rather than a proper Iridium plug.

I have the Mixture screws set to 1.5
I got 105 mains in but i think i do need to change them back to 100,
Needle is now set to highest clip (leanest). runs a bit better.
Floats and diaphragms are all good.

I been reading up and an over packed exhaust could be a cause? I got a standard end can that i have replaced the main inner tube (kept baffles in) and packing.

I have not given it a good run since I've had it back together (MoT on Friday). Hoping that a good run will settle it down. Need to give it a long run after that and check the valve clearances again.

*Edit* I also Un-plugged the TPS for the time being to also so less interference until i get it running better, Using the loom i got with engine but i fully replaced main power run with some Tri-rated cable. I am also running Stick coils which has noticeably increased the spark power.

I am certainly no authority on this but I have read some articles like this one
http://www.motorcycleproject.com/motorc ... coils.html
that cast doubt on the fitment of COP (Coil Over Plug) to something that was not designed for it.
In any case it is always good to question everything if your bike behaves differently after making several changes.
Do COP systems on modern bikes use a wasted spark? If not then is there any downside to connecting them to a wasted spark system? There does not seem to be much in the way of quality information on this.
cheers
Blair

I will have to give that a good read through when i get home from work,

I got the idea from Practical Sportsbike magazine, they did a feature on how to do it.
It is still running a wasted spark system as it is wired up the same, (1&4, 2&3) when i first did the "upgrade" on my old engine before it gave up the ghost (passing to much oil and covering plugs) i noticed an immediate performance improvement. I have also purchased another set for my zzr to convert.

Well that sounds encouraging. I always wondered how it is that they seem so small compared to the older coils. Did you have to get a specific ohm value to suit your bike?

What is the standard turns out on the pilot screws? How about your needles and needle jets, any wear on them?

There are a couple of things that can render Mikuni Carbs completely un-tunable. The most common of these things is worn emulsion tubes.

Friction from the needles can wear the original round holes in the emulsion tubes into an oblong shape (or maybe "oval" is a better word to use). This turns the bike into a rich-running pig and there's nothing you can do about it with tuning, the emulsion tubes have to be replaced.

From the Factory Pro tuning page: http://www.factorypro.com/products/Miku ... t_buy.html

(main Factory Pro page: http://www.factorypro.com/tech/tech_tun ... gines.html)

@LiteTekBlair I did not choose a specific coil to suit ohms, i just looked at what used the same spark plug, asked the guy on E-bay for the dimensions, and just bought some, they are from a R6 5EB model, they do stick up quite high but they have to otherwise you wouldn't be able to get the connectors on. If you wish can post pics of what i have done.

@SevenThreeSeven A good page that thanks just bookmarked it. I will have to take them apart again in the week and have a look, I feel that they might not be warn as before on the previous engine + exhaust it i just couldnt get it running rich, lucky it was burning oil for how lean my bike was running, i took it on the dyno and it was off the charts for how lean it was worse graph ive seen.


Took it to the MoT this morning, managed to get it there in this sweltering heat, pulled up, then all of a sudden pissed coolant everywhere, temp was at 3/4. but was a 6 mile trip, in heavy traffic, in English summer, was a tear in pipe i already replaced prev. now, did it overheat and cause that tear? does seem to run allot hotter then previous engine, but it is hot out....

After reading scottys thread i turned the A/F Mixture screws out half a turn so they are at 2 turns out now, seems to idle better now but still poo when trying to rev. just bout to go out for a quick spin now it is finally taxed and test again.

My gk71b ran rough for a long while and used to cut out without warning. Hot re-starts were always a problem until I changed the paired ignition coils with 954 fireblade stick coils after reading the same Practical Sportsbike article.

Now it'll start whether cold or at max temperature and the engine runs altogether better. I can't see any negatives to this upgrade. Sorry, this doesn't help with your carb issues........

haha np slabby is a worthwhile mod i bought another set as was going cheap.

Done 250 miles on engine so far and 3 dyno runs.

Really dosn't want to set off, having to really slip the clutch to get moving and its a bitch moving of on a hill :/ i am thinking this is a clutch issue? i may just throw my clutch in from my old engine as it will only take 20 mins. Or is this a trait of the SP gearbox? as i can really tell that this engine is SP, first gear is seriously tall, such a pain round town having a shorty lever.

Got 50.9 BHP @ the wheel but the power curve is shockingly bad lol.