4L0-00 or 4L0-01 Carbs.

[steven]

Hi,
I have almost completed restoring my 1980 350LC.
It is standard, on 1.50mm over size bore, the crank and re bore was done at PJME.
All new seals, gaskets, bearings etc.
Iv ultrasonically cleaned the carbs and re built them with quality parts.
Good set of reed valves, with new genuine Yamaha standard steel reed petals, and they are sealing perfectly.
I have pressure tested the crank case and cooling system, they are tighter than a crabs arse at 40 fathoms !...... after sorting all the leaks
The barrels are the "older type" without the 1 on them.
I don't know what engine number the barrels came off, as I bought them at a different time from the bike, All I know about them is that they are the "older type" without the 1.
My carbs are the 4L0-01 "newer type"
I do have a set of 4L0-00 carbs, I'm wondering what ones I should use?
I almost started it last weekend for the first time, but found something else to fanny about with on it, so didn't start it. This week I have been pondering about trying it on the older carbs first, as I'm sure I read somewhere that the "older type" barrels run better with the older type carbs?
It has standard exhausts.
It has standard ignition timing, set with a clock gauge, and I used two clock gauges to check the crank did not twist when everything was torqued up.
I have measured the squish band, it is as expected, a little wide, but probably no more than when it left the factory.
I have attempted to keep it as standard as possible, well engine wise anyway, in fact most of the bike is as standard as possible.
I was just wondering what carbs I should try first, if anyone had any thoughts?
Thanks in advance,
Steven.
PS, forgot to say, it will be run on premix, and I have upped the main jets two sizes......I have , probably, like most on here, seen the aftermath, and the big black mark on the road, from an oil pump failure.

[Deleted]

dont set the igition timing as the standard 2 degrees btdc, set it at 1.8 degrees btdc, as thats the best setting for unleaded fuel.
and i would use the later carbs

[arrow]

Any photo's of your bike?

[steven]

Hi,
Should I still adjust the ignition timming to 1.8mm BTDS if I will be running it on the super unleaded stuff?
I had read that it doesnt seem to go off as quickly as normal unleaded?, from what I read about "normal unleaded".... is that it has deed sheep and old rags floating about in it !
Should I get my clock gauge out again???
Not got any finished pics yet, as Iv still to send the body work away to be sprayed, and paint the exhausts.....and no doubt loads of other wee things.
I did make up a long airline the other day, and lead it in the house and blew all the dust off it tho

[arrow]

Standard bike with super can run 2mm btdc. Although the unleaded has sufficaint octane rating to run 2mm also.

[steven]

hi, glad to hear that 2mm btdc is ok something else i can keep standard,...id still be interested as what to go for with the carbs.... the new or the old ones?
Im fully expecting to be fiddeling with the carbs, but just wanted to start at the right place.
Iv not done a green olive nut and bolt type restoration, I just wanted to keep the engine as standard as possible, so as to have as little buggering about with it as possible once it was ready to go on the road.

[arrow]

I'd go with the later carbs. myself.

[muttsnuts]

ok, see my thread on better midrange.

What I can tell you for ceratin is the following as this has all been done on a dyno and validated

1. Timing - 2mm BTDC - running 1.8mm on a standard engine is a waste of time and you will lose some horse power and throttle response - I tested this on my bike using standard unleaded
2. Early barrels with later carbs is fine - that's what mine is running
3. Squish, don't about it, unless you are tuning it or going for better horse power standard is fine
4. At 1.5mm O/S I would go up to 230 mains and have the air screw set at 1 to 1 1/4 turns out
5. If you are running the standard air filter, then I'd have my needles on the 4th clip down (richer) to compensate for the larger bore at mid range
6. Do a plug chop after doing some running in miles and check them at different rev's, so 4k, 5k, 6k and 7k, or better still get it on a duyno once you've done sufficient miles
7. Don't run the engine on fiull synthetic 2 T oil, it will hamper the pistons, bores etc bedding in - semi is perfectly fine these days and fully is just overkill and unnecessary

hope that helps

[ianr4863]

I would use the 01 carbs . Yamaha had to do a dealer recall on the 00 . Somebody else will remember the exact details but it involved stopping up one hole with Araldite and opening up another with a 3mm drill . The later type had a factory modification done to them - not by the dealers .

[skaterboy]

Use the later Carbs there was a good reason Yamaha changed them .

[flames]

i would use the later carbs.then i would fish out my oil pump,send a pm to arrow,and ask about this oil pump re build service he offers.i bet theres nothing about the rd oil pump he doesnt know.he has the power to rebuild and make your pump as good as it was when it left the factory,only more efficient because he has fine tuned the settings to suit todays much improved oils.i shall be re fitting my pump with this rebuild.i am running premix at mo.i went up 2 sizes on the jets,but that was too much,i had serious bog @wide open throttle,i had to drop the needle a notch to compensate.my bike deffo ran better with the pump.

[steven]

Goodmorning,
Thanks very much for all the replies, looks like it is an overwhealming win for the later type carbs, thats what Ill start with then.
thanks again,
cheers,
steven.