250 LC running problems

[tunneruk]

Guys .......

Ever since I've had my LC it's had a running problem, it practically refuses to pull away under 5k revs, won't pull under 5k revs and struggles to pull top gear (I sit at 80 in 5th at 8k revs quite happily though)
It does however launch off like a scalded cat at about 6k rpm!

The bike is absolutely completely 100% standard and only on it's 1st oversize 0.5. I have just rebuilt it with all new bearings and oil seals so I'm confident of no air leaks.

Bores - Good
Pistons - New
Head - Standard
Porting - Standard
Carbs - Standard (2nd set tried making no difference)
Reed petals - Standard
Exhausts - Standard
Airbox - Standard (Including induction funnel present)
Air Filter - Standard
Timing - Set at -2mm BTDC

I don't suspect that it's running lean as the plugs and cylinder head squishes are a nice healthy dark brown.

So then brethren, pick the peanuts out of that!
Is there something obvious that I've missed or does all of the above sound about right? I'd absolutely hate to have to take it somewhere to get it looked at .... the ultimate defeat but it's go to the point where I've run out of ideas .........
I'm in Maidstone in Kent if there's anyone local that fancies taking a look for a few beer tokens?

Cheers in Advance

[foxyfeeling]

I have got a 250lc as well I had a bit of work done by taymar racing they have got a web site and they are just 15 minutes from brands hatch , my LC pulls like a train and when i put it on stinkwheels dyno even they were impressed by what it was kicking out for a 250 .
I would give him a call he is a nice guy not sure how far you are from him though don't know Kent that well
Rob

[wonkywheel]

Have you tried another coil?
It's a long shot, and might not apply to motorcycle coils. Some coils have primary and secondary windings. One for low revs and one for high revs. Maybe the primary windings are breaking down.
Like I said, a long shot.
Good luck.

[marsbar350]

is there a lot white smoke comin out of either exhaust?
could be a crankseal
was it fitted the right way round?
tighten all your clips again carb to inlet rubbers etc.
andy

[Delbert]

I guess you have the carb slides in the correct way round Taper towards the air intake,, just a thought !! Classic symptoms

[tunneruk]

Dec 1, 2012 18:04:09 GMT 1 Delbert said:

I guess you have the carb slides in the correct way round Taper towards the air intake,, just a thought !! Classic symptoms

Yup .... all present and correct!

[tunneruk]

Dec 2, 2012 7:21:50 GMT 1 butchers said:

You've not mentioned what settings your carbs are set at.
if ya have problems pulling away suggests you may need a bigger pilot jet

it also seams like its overfueling until there enough force to clear the system @8k when everything is balances out

Ok, I'm very mechanically inclined and I have a very decent understanding of fuelling etc but there's a point where my knowledge ends ....... I'm at that point!

So it's possible that I need larger pilot jets but it may be over fuelling ................. I'm consufed?

[tunneruk]

Dec 2, 2012 11:20:54 GMT 1 butchers said:

hopefully this may help you i saved it from an earlier post by someone on the forum

That sir is bloody spot on!

Looks like I'll be stripping the carbs and upping the pilot jets!

Question is ...... by how much??

[oldelsieboy]

There is a Mikuni Tuning Manual available to download HERE

OEB

[artie]

Check this out mate,you may find it interesting
rdlccrazy.proboards.com/index.cgi?board=mods&action=display&thread=18087
There seems to be various schools of thought on the 250LC,mine is totally standard and to be honest feels a bit flat up to 5k then stutters a bit then as you say takes off like a scalded cat,some say they are all like that,some say it can be sorted,I,m hoping to get mine on a rolling road in the New Year so we,ll see

[tunneruk]

Sussed it!!!

Sometimes the simplest things can make all the difference. I figured that before I blindly start buying various jets etc I'd have a quick look at things I can change immediately.

So I popped the carb slides out, lifted the needles by 2 notches and hey presto ...... she's smooth like butter!

Amazing how the tiniest thing can make such a difference ah!

Just wanted to say cheers for all the replies and suggestions :thumb2