Project 3LN1 Restoration

They should both be cup seals. The one on the right looks ok, the one on the left looks worn down.

 

I'll send you the whole shebang, the whole master cylinder, as I've no use for it

It will need a clean, but isn't seized

Will scout around for it tomorrow

 

@maelstrom will let you know exactly what the differences are between the o-ring sets for the carbs are, however I think it may be only the jet housing seal

 

Exactly the same engine, there are some small jet type changes from 3LN1 -> 3LN3/5 but the fueling requirements are identical

 

From this post

https://www.2fiftycc.com/index.php?threads/first-bike-the-fzr250-3ln.10816/page-3#post-130275

which links to this post

https://2fiftycc.com/index.php?threads/my-fizzer.872/page-32#post-15537

You'll be measuring and adjusting the float height to effect a change upon the fuel level

You will be aiming for 16mm float height, which should yield a fuel level of 9.2mm

A great suggestion that I read, I think @my67xr, was to use a jewellers screwdriver, into the small metal tang on the float to make the adjustments, that way you can leave it all in place

Also leave the needle & seat valve alone i.e. still fully seated when you remove the float bowls to make the adjustments

As you are not certain which series carbs you have, just check the main jets;
3LN1 will have 100 on carbs 2 & 3 and 102.5 on carbs 1 & 4
3LN3/5 will have 97.5 on carbs 2 & 3 and 100 on carbs 1 & 4.

As for anything else, just leave it be for now as you've got fun stripping and cleaning when your litetek seal kits arrive and dong the damn things is only fun once - trust me

 

There are some outward differences between the 3ln-1 and 3ln-3 carbs, I have a set of each out in the shed......the only problem is the shed is currently over 100km's away.

From memory, and it has been a couple of years since I was working on them, but in addition to the idle screw, a big difference was to do with the throttle cable mount fixture in the middle two carbs.

They changed the design because when you put the long screw through the mount in the 3ln-1 carbs it was easy to crack the casting in the diaphragm area of one of the middle carbs when you were tightening it up.

I think, and obviously I cant confirm since I don't have them at hand, that the later carbs had a lug cast into it to accept a hole in the mount and stop it from cracking.

I also remember there being outward differences in the float bowl castings between the two sets of carbs too but cant remember the details, I'd need to have them in my hand. The bowls both interchange freely but there was a visual difference if i'm remembering correctly.

 

Yeah I gave up using the float height method on anything other than vertically mounted carbs for the very reason you’ve stated above. Some people can do it, but I’ve accepted that I can’t.

I mark the float bowl at the correct height and use the clear tube method. This can be done with the carbs mounted on the bike except for the no.4 carb for which I found one of the float bowl screws to be unreachable once mounted on the bike.

The easiest way to deal with that one is to do it first. I think I removed the float and adjusted it in one of the other carbs first then swapped it back in and tested it, it didnt need much if any adjustment once in place.

 

For knowing the angle that the carbs need to be on, it's the angle of the dangle - the float needs to swing and just be touching the float needle and NOT compressing it.
It isn't too difficult to achieve and isn't overly precise as the spring does have some resistance to being compressed obviously.

EDIT - To answer your other question - I had made a wooden stand to replicate the angle of the carbs on the bike, because I was chasing the wrong solution to the fueling problem at that stage - it was for checking the fuel height.

At that point in time we had misdiagnosed the low RPM chugging as leaking needle seats, we were yet to learn that the issue was worn emulsion tubes.

Adjusting float heights, which is the pic you see with the playing card has the carbs at an entirely different angle to how they are on the bike, and I made the wooden stand to be reversible so that one way I could measure fuel height and turn the carbs 180 degrees to adjust the float height

So much time chasing the wrong cause...

I commend @beano for managing to do the adjusting with the carbs on the bike - that's impressive and does speed up the fuel height measurement

Note that @beano is adjusting the floats, THEN checking the fuel height, he's not adjusting the float tang and then measuring the float height

Both methods will have their benefits - take your pick

I will say that likely you will need to remove the carbs once to replace the remove the fuel bowl screws the first time, if they are still screws, you won't get enough purchase, but if they've been replaced with allen key bolts, which will be more easily removable definitely - try the @beano tech first