Jetting starting point for a 4L0 350lc with 31k carbs

[alankelly]

Hi all.

just starting my engine rebuild for my project over the next few months, and need to also start the rebuild the carbs, so after some advice please?

The bike itself was a bit of a basket case, and was a non runner fitted with a very "white and fluffy"  4L1 L/H carbs and R/H 4L0 carb?? And on closer inspection both carbs had some parts missing such the slides, springs needles etc so managed to source a pair of complete clean 31k carbs.

I know it seems reading on the forum each bike seems to be an individual as per jetting selection. But to give me a starting point for my carb rebuild, would anybody be able to advise what I should start with please? pilot size / main needle size,  needle and clip position,  float height air screw turns out etc etc

As for the bike itself the engine will be of a standard tune with the stock filter / air box / snorkel (Yes I can hear the objections already!!!) And the only non stock part is I have fitted a set of Higgspeed GP pipes as the other they came with the bike were past it.

Any help or advice most welcome.

Lastly great forum guys, and thanks in advance for all the advice past present and in the future.

Best regards Al. 

[Dangerous]

Best advice I could give regarding ya carbs, send them to mutts nuts on here, top bloke and does a great job .👍👍🏍

[dusty350]

Hi Alan
Not sure what jetting mods the Higgspeeds need - some pipes do and some don't but usually swapping from an airbox to pod filters makes a huge difference to jetting.
I had a standard Lc with airbox and Allspeed small can pipes, and I fitted 31k carbs which are known to work well on the Lc. I used standard 31k main jets, but research suggested upping the pilots to 27.5's which I did. I sold the bike once finished, but the new owner has done over 400 miles on it and says it fuels really well with no issues, so as long as your Higgspeed don't need larger jets, you will probably be about the same. As always, tread carefully with carb settings, and get expert advice if unsure - Muttsnuts is our resident "guru" and sorts lots of carb issues for people

Dusty

[alankelly]

Hi dusty

Thanks for the info

I did question Dave at high speed and he said with standard air box etc his pipe should run with normal jetting but will be cautious and maybe contact muttsnuts

Thanks again alan

[4l04ever]

The standard 31K carbs have 240 mains rather than 220 for the 4L0-01 carbs. Needles/pilots/slide are all the same as 4L0. Make sure you blank off the vacuum tap feed.

Someone on here had issues with running Higgspeed pipes and I think they ended up selling them on.

...just found it....
rdlccrazy.proboards.com/thread/44791/higgspeed-expansion-pipes

[alankelly]

Hi thanks for the possible Higgspeed issue

Unfortunately I cannot open the thread but do you know what the issue actually was please?

Thanks again Al

[mt]

Oct 16, 2018 20:58:47 GMT 1 alankelly said:

Hi thanks for the possible Higgspeed issue

Unfortunately I cannot open the thread but do you know what the issue actually was please?

Thanks again Al

splodgey Avatar
Jul 18, 2018 20:00:28 GMT 1 splodgey said:
Hi everyone , I have a pair of stainless steel Higgspeed expansion chambers for sale to fit a RD250 / 350 LC . I fitted them and used them for a short run out but they are not for me ( too loud ) and bike needs re jetting to run properly,They are still in the original box and are like brand new . I am asking £400 for them or near offer and can deliver locally to Stafford . Postage would be around £25 but prefer to sell them locally if possible. Great looking pipes without the 12 week wait ... Thanks Dave Whitlock...


Copied and pasted for you 👍🏻

[alankelly]

Thanks for the copy and paste

Better buy some earplugs but looking at the GP pipes with straight thru cans I recon they would be loud and the bike my need correctly setting up

But thanks for the heads up👍

Best regards Al

[alankelly]

Hi all

Dusty has suggested I fit 27.5 pilots to my 31k carbs which sounds a good idea as would rather err on the rich side to start with

Question is where is the best place to source individual pilot jets needles and main jets etc please as separate items once I am in a position to start my carb build
Thanks for all your help in advance Alan

[dusty350]

Hi
I should have verified that I meant the standard main jets for the 31k carbs, which are 240's. I read a few threads where guys found the bike to run better with bigger pilots so that's what I did, and as said it fuels really well. Norbo sells jets, or Allens 01949 836733.

Dusty

[alankelly]

Hi Dusty

Thanks for the info

Best regards Al

[alankelly]

Hi all

Just started the check out my 31k carbs for jets sizes actually fitted before I order the correct sizes and am I right that unlike the earlier Rd350lc 4l0 carbs, for the 31k type each carb has is own tank connection rather than that link pipe between the two carbs for the 4l0 with just one tank connection to the l/h choke” carb

Also where please is the vacuum take off i need to blank off I presume it’s on both and it’s the 6mm connector that when you blow thru you blow air into the main Venturi

Thanks for all your help in advance

Best regards Al