Another jetting question - even with pichkers! :)

[strom]

As some of you guys know, my 78E went to a new home, where it was almost completely restored to a level I never thaught possible.

Anyway. the bike went to a friend who lives near-by. We swapped the bottom half of the engine case, replaced some cogs in the tranny, put some new seals in, the engine was sandblasted and painted,....

With all that the carbs were cleaned to perfection, they also got new intake rubber manifolds and new diaphragms.

We set the float height per factory instructions, so are the main jet needles.
All jets are stock, so is the airbox and air filter. Exhaust headers are custom made 4-2 with x-over.

Pilot screws... were a bit of a problem. Long time ago someone screwed them in too tight and the tips broke off. I had to hammer them out and did some damage to the inside of the carb. It was the only option back then, but there we are. I got new screws, put them in and set to what felt right and rode the bike for quite some miles without hassle, only a bit high fuel consumption (24 mpg vs 31 on my other XS).

Now, when he was doing the cleaning etc etc, we completely dissasembled the carbs, put them back together and synced them, set the idle screws in till it almost died, turned them out till it worked real well and half a turn extra out.

Re-synced the carbs, set the idle screws so the vacuum gauge needles would rise to the same level when given some gas, and dropped in sync when it dropped to idle.
Re-synced the carbs again.

The annoying thing:
Doing anything with #1 idle jet screw had no effect. At all. Fully in ran just as fine as anything.

The bike stutters up to 3k rpm under acceleration, above that is OK.

Heres the plugs:




So, any ideas?

[strom]

Now I know some of you were wondering, how does sandblasting and painting the XS engine look like:

before:


Blasted:


Painted (not yet unmasked, but fins polished):

[petejw]

hi strom,
is this the engine u stated in the honing thread
that was rebuilt?

most problems ive found with the engine playing up
under 3000rpm have been either float levels or
idle circuit problems, if its carb related,
but if you've enlarged the hole where the mixture screw goes
in that could also cause a problem.

also had problems if the valve clearances werent right, ( i had 3 closed
intakes, bike seemed fine over 3000rpm but was sluggish under it)
was the head serviced? (valves lapped etc)


btw, that engine looks real sweet.

[kirmit77]

More details on what you used to blast and paint with please!

[strom]

Yep, this was the engine, that was rebuilt.

From what I can remember from the top of my head:
I got the bike in boxes. PO said the engine was not open, but I found some stuff that indicated otherwise.

Anyway, I changed 2nd and 5th gear cogs for new items that came with the bike. Also the camchain and primary chain.

Replaced #3 cyl valves and we messed up cam timing a bit. Only those 2 valves were slightly bent.

Replaced valve stem seals, 4 idle mixture screws, put repair kits in carbs and petcocks.

Honed the cyls, replaced piston rings, lapped and set the valves.

Made new 4-2 exhaust headers and mufflers.

Replaced middle drive bearings, new oil seals and other rubbery stuff everywhere.

Painted the gas tank, replaced instrument cluster.

Replaced middle drive a bit later on, all in all the bike did bout 20.000 miles since I got it. Maybe a bit less, maybe a bit more. Then I got a parts bike and I sorted that one out, since it was in way better shape. This one sat for a few years, then I sold it to a friend.

The valves are fine IMO.

He replaced a bunch of stuff described in the first post.
I will ask about the blasting agent used on the engine. He used some quality paint on the cases and high-temp paint on the cyls/head to paint the engine.

This is carb related IMO and I have no idea on how to properly sort out those idle circuits. Basically I was just asking, whether it is the idle circuit or the float height? Since its fine above 3k rpm, I would think the float height is fine. But looking at spark plugs, what would the gurus do?

[ManagerMike]

It looks like #1 is lean as hell, and you said the #1 pilot screw has no effect regardless of where it is adjusted, and it performs poorly through 3000 rpm (pilot circuit range). The only thing I can come up with, given that info, is that there is blockage somewhere in #1 pilot circuit.

[strom]

Thanks Mike!

I will tell my friend to poke around there some more.

How bout the other plugs? They look beyond rich or am I totally wrong?

[natemoen]

I wouldn't say 1 looks "lean as hell" the electrode and ceramic under it are brow to black. I would think 1 and 2 are a little rich, 2 more so, and 3 and 4 are quite a bit more rich. does it run well still?

[strom]

Above 3k it runs like a champ. We will see what happens if we turn in idle screws a bit. And check that #1 for blockage or something.

[petejw]

hi strom,

with the new rings being fitted, does the engine blow smoke,
if so, then reading the plugs makes it more difficult, my plugs
looked like that when the engine was running lean, mine blows smoke,
in saying that the plugs should at least all look the same.
my bike does the same thing but it does it on no 4 cylinder, it has
done it with 2 sets of different carbs, the stock mikunis and the zxr carbs
im running atm, the only thing i couold put it down to was that no4 cylinder
has a valve that seaps ( which i knew when i put he head on ) , so when i do a sync that butterfly on that carb
is slightly more open, so its picking up extra fuel from the off idle ports,

can u sync the carbs on the bike whilst its running, then remove them, put the carbs up 2 sum light and see if that butterfly is open more compared o the others,

after u replaced the valves did u do a seapage check? (pouring petrol into the ports to see if they leak)

also u stated u replaced the bottom half of the engine case, these cases are a machined fit and should be replaced as a pair, not much u can do bout that now, just sum info i thought u might like to know.

[strom]

Heya Pete....

No smoke.

Cases should be machined as a pair, but are prolly not. We measured them... were bout 0.005mm apart, but in horizontal alignment. We fixed that by removing a centering stud thingie, that was a bit bent. So no problems there.

Good idea bout checking the butterflies.

[petejw]

blowing no smoke is a good sign at least,
in know un said u set the float heights at stock
but what did u measure them at?
how does the bike ride with the same throttle position to where its
playing up at off idle but in a higher gear at higher revs?
sometimes it can make it easier to determine if ur running rich or lean.