Went down to the shed today. . . .

[jonno]

And found my 1980 RD350LC that i had forgotten about!

I gave up on it last time as it was not running right on the right hand cylinder and would not pull past 7000 rpm on the road and i was right pissed off with the number of times i had stripped and cleaned and rebuilt the 4LO-01 carbs with out much success.

To recap the motor has a had a full rebuild and is in standard trim.

Today i removed the head and barrels for lapping and to make sure that the cylinders were of the same height (which they were). I removed the pistons to remove the tab at the bottom that can apparently catch the inlet port with devastating results. Fitted it all back up and she started up on choke and settled down to a nice idle whilst warming up. The exhaust pressure still seems a little weak on the r/h cylinder though the engine revs freely on the stand with no misfiring or spluttering.

Tomorrow i shall re-torque the head bolts and take her for a test run on the road to see how she behaves.

I am now 100% sure that the running problem is NOT due to mechanical or ignition faults so the problem has to be with the carbs.

Has anyone had any experience of having carbs ultrasonically cleaned?

I will update after tomorrows road test. lol.

[ozzy]

how fars ya shed... ;D to forget a rd350lc.... ;D

[jonno]

Well after re-torquing the head bolts down, i took the bike for a road test.

At first it struggled to pass 4000 rpm and after a short while it would rev to 6000 rpm but no more!

Starts fine, idles fine, revs fine with no load, crap on the road spluttering at 4000rpm requiring the throttle to be let off and then it can be gradually coaxed to 6000rpm.

All in all, about as much fun as a puch maxi!

What do 350lc's make on E-bay these days?

Not sure whether to strip and rebuild the carbs (AGAIN) or buy another set and rebuild those a few hundred times instead.

[elsie1411]

mate it really sounds like a twisted crank, but i will stand corrected but sounds exactly like mine.

[Norbo]

The only unexpected things i fined in my shed are spiders.

[rev1961]

Purposely lost mine in the shed as well for the past year

Same problem !! Totally pissed me off. I got a full crank rebuild and a rebore. Replaced all the jets(standard) in the 4L0(01) carbs. Got the carbs ultrasonically cleaned. Replaced the coil & put in new plugs(B8ES). Even drained the tank. Still after all that the problem remained.
Decided to put a pair of 31k carbs on the bike. Same problem existed.
A mate of mine is also running his 4L0 with 31k carbs, and it's sweet as a nut. I decided to check his jets etc. His carbs were running on a 230 main jet, whereas mine were running on a 240.
Bottom line, I replaced my jets with 230's and hey presto she's on the button and threatening wheelies ;D ;D

Note. most of the engine work was needed, so not a major waste of money.

Would it be possible to increase/reduce the jet size in the 4L0 carbs to sort the problem ?

[lcowner]

ah welcome lad......dont have a clue but someone on here will!

[jonno]

To: rev1961,

I am running standard jets on 4lo-01 carbs and standard silencers.

What exhausts are you using?

My engine seems to run weaker on the right hand cylinder and the plug appears wet and oily. (It makes no difference if i change the plug leads over so its not an ignition problem).

Did your bike run worse on one cylinder, or both before you reduced the main jet size?

Cheers.

[jonno]

I just thought!

Instead of dropping the main jet down one, i could fit my allspeeds on and see if that makes any difference? ;D

[rev1961]

I actually changed my pipes to 31k. Had been running on 4L0 standard. The problem had been present on both pipes with either 4L0 or 31K CARBS.
I was also having a problem with the plugs especially the left side (sitting on bike). I changed the plugs from BR8ES to B8ES. This sorted the fouling as the B8ES burns the mixture more easily (or so I'm led to believe).
A change in the pipes may be your solution, but doesn't satisfy a 'bog standard' preference.

Are you certain your standard pipes are 4L0 (stamped 'O' on hanger) or possibly 4L1.

[Norbo]

Sept 15, 2010 0:49:28 GMT 1 @ravedaddy said:

................... went to the pub, best idea ive had in ages, gonna stay here till me kidneys run out.

Dood you make me piss some times LOL
That F1 looks minty clean

[jonno]

Sept 15, 2010 0:11:28 GMT 1 rev1961 said:

I actually changed my pipes to 31k. Had been running on 4L0 standard. The problem had been present on both pipes with either 4L0 or 31K CARBS.
I was also having a problem with the plugs especially the left side (sitting on bike). I changed the plugs from BR8ES to B8ES. This sorted the fouling as the B8ES burns the mixture more easily (or so I'm led to believe).
A change in the pipes may be your solution, but doesn't satisfy a 'bog standard' preference.

Are you certain your standard pipes are 4L0 (stamped 'O' on hanger) or possibly 4L1.

Cant be 100% sure on the pipes (E-Bay Specials! lol). I need to remove them and have a closer inspection, it could be that one of them is restricting the flow more?

By the way, the standard main jet for a 4lo is 220 so you are running richer on a 230 with standard set up.

[rev1961]

Sept 15, 2010 8:20:58 GMT 1 jonno said:

Sept 15, 2010 0:11:28 GMT 1 rev1961 said:

I actually changed my pipes to 31k. Had been running on 4L0 standard. The problem had been present on both pipes with either 4L0 or 31K CARBS.
I was also having a problem with the plugs especially the left side (sitting on bike). I changed the plugs from BR8ES to B8ES. This sorted the fouling as the B8ES burns the mixture more easily (or so I'm led to believe).
A change in the pipes may be your solution, but doesn't satisfy a 'bog standard' preference.

Are you certain your standard pipes are 4L0 (stamped 'O' on hanger) or possibly 4L1.

Cant be 100% sure on the pipes (E-Bay Specials! lol). I need to remove them and have a closer inspection, it could be that one of them is restricting the flow more?

By the way, the standard main jet for a 4lo is 220 so you are running richer on a 230 with standard set up.

I ran the 4L0(01) Carbs with the 220 jets. Am running the 31K carbs with 230 jets, down from 240.

[jonahlc]

weny down to shed today some f***ers nicked it.
why didnt they take the wendy house and the bmx instead

[bubba]

;D ;D iy very funny that ;D ;D

[daveg]

you don't mention having changed the plugs..... I assume you have?

[nikfubar]

Sept 15, 2010 0:46:15 GMT 1 @ravedaddy said:

went down to the shed today.........found this f**king cbx in there .................went to the workshop.

Rave
Do I spy an NC35 front wheel at the back of your shed ;D as I'm after a straight one if you fancy selling it

[mellow]

f**k me nik u got good eyes m8 ;D

[jonno]

. . . . . . . . . . . Kicked my LC, locked the shed back up and threw away the key! lol.

[fazerman]

sounds like my first lc ,.would tick over fine ,rev up nicely in
neutral but would f**k about under load.
wouldnt rev above 5000.
turned out to be the stator breaking down at high revs
just a thought.......
new stator bingo!!!!

[pepsisteve]

just book it in for a dyno session mate, i'm sure they will put there finger on the problem.

[par6]

Have you balanced the carbs with the lollipop stick method ? Transformed mine

[jonahlc]

its back its back it was all a bad dream

[Norbo]

LOL

[nikfubar]

THERE'S SMOKE COMING OUT OF IT LOOK OUT IT'S ON FIRE ;D

[Deleted]

Bad earth? I've had that before and a clean up solved a very similar sounding problem on my old KR1.

[jonahlc]

?

[scott]

that poor lc with the shame of being parked up next to a suzuki ;D

[jonahlc]

its a breeding progamme

[jonno]

Oooops!

I forgot to close this thread.

I replaced the loom, stator & fitted gen Mikuni jets to the carbs and it runs like a dream now.

Thanks for all your input, (and photos of your shed's ).