Pilot Needle jets......

[Suzuki Mad]

OK.

This is a discussion, not a 'I know, I'm the expert' sort of question and definateley not a chuck your toys out of a pram thread!

Ground rules out the way here goes.

Mikumi BS34SS carbs. I had pulled my GS1000 carbs and Londonboards had kindly stripped, ultrasonically cleaned them plus rebuilt last week. Thank you Londonboards. I also have a little incling as to whats inside them.
He pulled the Pilot Needle jets out. Those long pre set jets that come done from the factory and 'never to be touched by human hand on pain of death' according to all the bike dealers of the 1980's. (Well we were told that these GS engines would never last more than 20,000 miles before blowing itself into small pieces.)

So these are part no 13279-47080 pilot needle jets.




Suzuki didnt give a part number for these delightful little bits back in 1980, it came with the carb. But they look identical to what is in my GS1000 carbs. They even fit!

In 1984/5 Suzuki started to give part numbers for these items on the GSX1100EFE.




I believe that is one above. (Happy to be proved wrong.)

My GSX1100ESD carbs needed Ultrasonic cleaning so I was lent the cleaner and do it myself as I had watched how to do it.....

Now inside my GSX1100 carb are these.



Please excuse No 2, thats what I had to do to get it out.

You will see that there is a long shaft for the spring, washer and O ring to sit on and the tip is step tapered and no point against the GS1000 one that is a taper to a point. Does anybody know why? Can you swap them and will it work?

I had a heated discussion with a carb rebuilder yesterday who claimed that all 4 of the GSX1100 ones were damaged as 'they should all have tapered points.'

I posted on here to find a replacement from a damaged set of carbs or carb and somebody found this one.



Step tapered like my GSX ones but a little shorter.

When you look around various carbs have various needle pilot jets and not all go to a tapered point.

Suzuki also do this jet. 13279-47070 a later shorter replacement for 13279-47080. It fits most Suzukis from the 1990's through to the 2002, so in my RF900 and also my GSF1200 bandit Mk2, (Add in GSXR600, Mk1 Bandit and a load more.)

I want to learn here guys. I'm trying to understand why these are different and what will work.

Questions.
So why were my GSX1100ESD Pilot needle jets step tapered and not to a point?

Will the long GS1000 ones with a point work on my bike?

Why did they shorten then? (Stop them seizing up in the carb? )

Will the shortened step tapered one work in my bike OK? Has anybody else fitted one?

Cheers.

[GregT]

My understanding of the timeframe is that the first pilot jet circuits had the pointed needles and small holes in the carb bodies.

As time passed, it became obvious that the small body holes (fixed jets) were prone to blocking.

The cure was bigger fixed jets and a non-pointed adjuster needle.

This sequence appears to follow across VM and CV carbs. I go back far enough to have worked with early VM's on race 2 strokes and saw the change with later bigger VM's.

I would assume (dangerous I know...) that you can't use the bigger, non-pointed adjuster needles in early carbs.
But if you have carbs using the bigger adjusters, the parallel length of the screw body should be irrelevant.

Anyone who knows different is welcome to chime in.

[Suzuki Mad]

My understanding of the timeframe is that the first pilot jet circuits had the pointed needles and small holes in the carb bodies.

As time passed, it became obvious that the small body holes (fixed jets) were prone to blocking.

The cure was bigger fixed jets and a non-pointed adjuster needle.

This sequence appears to follow across VM and CV carbs. I go back far enough to have worked with early VM's on race 2 strokes and saw the change with later bigger VM's.

I would assume (dangerous I know...) that you can't use the bigger, non-pointed adjuster needles in early carbs.
But if you have carbs using the bigger adjusters, the parallel length of the screw body should be irrelevant.

Anyone who knows different is welcome to chime in.

Thanks Greg T.

I'm only old enough to have ridden then back in the day and the bike went to the garage to be worked on.

[EDGECRUSHER]

Just to clarify;
Are you talking about pilot jets or idle mixture screws? Because those are idle mix screws in those pictures not jets.

[Suzuki Mad]

Just to clarify;
Are you talking about pilot jets or idle mixture screws? Because those are idle mix screws in those pictures not jets.

Thanks for the clarification, EDGECRUSHER.

People call them lots of different things so I am finding....

I need one thats in the photo, whatever they are.....

[EDGECRUSHER]

Unfortunately terminology is extremely important when discussing carbs and getting the correct responses. As far as what you have, I would err towards replacing with exactly what came out. Having said that, if you absolutely can’t determine what your carbs take by looking at the surfaces they mate with inside the carb, I would bet the non stepped screws might work the same depending on how much you end up screwing them out. The important part being the length and the angle of the steps.

[EDGECRUSHER]

After a little research I found most Suzukis with mikunis use two different part numbers for idle screws, both are not stepped. Kawasakis used a stepped screw but they generally run Keihin carbs. Is it possible someone replaced your mikuni screws with keihin?

[EDGECRUSHER]

I’m trying to help you figure this out but I see how hard it is to find. It’s not listed in schematics. Oh and it’s truely called a pilot fuel screw. Calling it an idle mix screw can get it confused with the idle speed screw. When I do a search for your model and I’m guessing it’s an 83’ish, I get several different styles listed.

[Suzuki Mad]

I’m trying to help you figure this out but I see how hard it is to find. It’s not listed in schematics. Oh and it’s truely called a pilot fuel screw. Calling it an idle mix screw can get it confused with the idle speed screw. When I do a search for your model and I’m guessing it’s an 83’ish, I get several different styles listed.

Thanks EDGECRUSHER.

Yes, they are not listed on the fiches for this model and also the GS1000 fiche I have yet people seem to find them.

Its a 1983/84 model only made for that one year and then dropped. People didnt like the style of it I suppose.

It is very possible that somebody else has been in here before me and changed them. I can only go by what I took out and as the part isnt listed I can only say 'thats what was in there.'

Its strange that on several Ebay listings people have listed GS(X)1100E pilot fuel screws as this step tapered version. Its where I took a few photo's from as examples. I have 4 long silver ones here that I can refit back in. However I would need advice as to the settings as they are very different to what came out and therefore the different ones might need a different setting to be close/right.

[hampshirehog]

There were 2 different types, as Greg said earlier, and you've posted pictures of both. If you had your bike running properly before with those fitted it will run properly again if you refit them and replace the u/s one like for like.

[Suzuki Mad]

There were 2 different types, as Greg said earlier, and you've posted pictures of both. If you had your bike running properly before with those fitted it will run properly again if you refit them and replace the u/s one like for like.

Thanks HH.

The issue is finding one so I can replace like for like. That is where I need the GS resources help to find one if at all possible.

Looks like they only come out of GS/GSX1100 carbs.

[hampshirehog]

You could carefully cut off the damaged top of your screw and cut a new slot for the screwdriver.

[Suzuki Mad]

You could carefully cut off the damaged top of your screw and cut a new slot for the screwdriver.

Good idea HH but sadly the damage is too much for it to go back in.

I'd PM you and explain more but your inbox is full.

[hampshirehog]

Good idea HH but sadly the damage is too much for it to go back in.

I'd PM you and explain more but your inbox is full.

i just deleted a load