The smaller jet I believe, in the carb does what?

I am wondering when cleaning the carbs where when you spray carb cleaner through the jets, where the fuel is supposed to go in the smaller jet. Or what I believe to be the smaller jet. I was wondering because when I spray cleaner through the large jet it comes out in a strong stream right in the middle of the piston. But where does the fuel go in the smaller. I don't see it coming out. So with that said it must be clogged or? I have a issue in transition from idle to higher Rpms. For example when its idling its great. Runs strong. Then applying throttle there is some hesitation and then once it get through that it takes off and really sound like it is running clean.

Someone please if you can explain to me the purpose of the smaller jets and if that where I should start or if there is anything else off hand.

Thanks

 

yeah if the cleaner doesnt come out the other side you've got a clog. I poked around in my carbs with welding tip cleaning wires to get as much loose as I could, alternating between poking and spraying with carb cleaner. Worked out ok for me =)

 

i doubt you will be able to get enough cleaner to flow through the PILOT jet, it is a very small orifice, and handles idle-1/4 throttle. technically it has an effect on the entire rpm range, but is very insignificant even at 1/4 throttle.

 

Yeah it just seemed like its not getting all it needs from idle to about 4000 and then the thing jumps in RPMs like it just found a spot of nitrous. However, I believe its just skipping the small jets and jumping to the big jets effectively. I'll be removing the bowls hopefully for one last time here and seeing what exactly is the deal with the small jets.


Thanks for the info.
I'll post the results tomorrow probably.

 

There's always Fuel being added to the Total Mixture by the Pilot Jets.
Although it really ain't much; you need the flow to have the Bike Perform right.

The Pilot Jets control Idle.
When the Throttle are closed the Pilot Jets keep the Bike running.
Additional Richness from the Pilot Jets (Supplemental Richness) is needed to
prevent the Bike from hesitating when the Throttles are opened.

The Supplemental Richness Fuels the brief period where fresh air NOT carrying along any Fuel -- yet ... enters the Combustion Chambers ahead of the Main FUEL Jet Supply.

When the Throttles are cracked open ... the in-rush of Air needs some FUEL.
It gets it from the Pilot Jet Supply.
Three scenarios are possible depending on how well adjusted the Pilot Mixture Screws are adjusted.

1) Too LEAN

The Bike will Idle fine.
The Bike will not "Get-out-of-the-hole" without hesitation or backfiring.
There is no a seamless transition from Idle to "Off-Idle" as the Throttles are opened.

2) Too RICH

The Bike will Idle but often without a confident-sounding steadiness.
The Bike will not respond well Idling when warmed-up.
Throttling-up to keep the engine running is often very necessary.
Coming "Off-Idle" and accelerating from a stop is difficult.
The quantity of Supplemental Fuel along with the Pilot Mixture is too Rich for Ignition. The Engine "Boggs-Out"
In some cases the Engine will STALL.

3) On The Money! (A "Window" of Fine Tuning)

The Bike will Idle like the Atomic Clock.
A seamless application of power allows for excellent performance out of the hole.
No Hesitation or Bogging.

Supplemental Pilot Mixture deliberately LEAN:
Speed and dramatic "Engine Braking"

Supplemental Pilot Mixture deliberately RICH:
Velvety smooth acceleration with Engine Coasting.

 

I had the same issue with the pilot jets. No low idle below 2000 rpms. I pulled them out and cleaned them with alcohol and a small strand of wire. A sewing needle is too big for the hole. I got the strand and kept twirling it until it poked thru. Alcohol gets right thru the varnish that sat for 18 years.

 

If you run-over to a well stocked Hardware Store; they'll have just what you need to clean the small Metering Ports of the Jets.

Buy a: Welders Torch Tip Cleaning Set.

You'll find a tool within the variety of wire tools supplied in the set to clean every orifice on the Carbs.

Bring a 5-Dollar Bill ... you'll get change!

 

I definitely already have a torch tip cleaner so thanks for that idea. I have two bikes now thanks to this site I am aware that have issues. This bike which is an 82 xj650 and the other one which is an 83 xj750mk.

I thought the 750 was running well but now I am realizing I have issues. Lean conditions by the plugs in 3 out of 4 cylinders. White tips on the plugs and on one plug kinda a chocolate color which seems to be good due to what I am reading. The pilot screws have not been opened or adjusted as this bike only has 13000 on it. They still have the caps. How would I adjust the other cylinders to match the chocolate color plug to keep from melting pistons. Realistically the bike seem to idle great and does have some hesitation in lower rpms and that clears up at higher rpm. Apparently its not rich because of the plug conditions.

How would I fatten up the mixture without disturbing the pilot screws or would that be the easiest way to tune this monster up. I thought it was running great and from what I am reading there is a lot more great to be had. No air leaks to speak of and i have never been through these carb.

Where should I start. extracting the caps to access the adjustment screws? or would there be something obvious in the carbs that would cause this lean condition? I am open to all options as I just want to do whats best for the bike as far any adjustments are concerned.

I will clean thoroughly the pilot jets tomorrow and see what that does. I have yet to find anything resembling dirt or contaminant in these carb on the 650. I have never opened the carbs on the 750.

I am fairly new to motorcycles and really new to XJ's But already I am fascinated by these machines. I build custom cars and street rods and high end performance cars for a living. Its great to have something this much fun to work on and this web site is making my experience extremely enjoyable and challenging. so thanks to you all.

 

I also use acupuncture needles. They come in very small sizes and are sharpened with fricken lazer beams. That is sharp.

 

A bike that hasn't had the caps for the pilot adjustment screws removed. Should I assume that there is another issue if its running lean or should I not worry and take out the slack (the lean condition) with the pilot screws. It leaving the plugs white in 3 cylinders so should I look for an issue in the carbs or just go for the un touched pilot screws?

 

By now, everybody should be aware that it is necessary to remove the Blind Plugs and have access to the Pilot Mixture Screws to do the Fine Tuning that will need to be done to make the Bike run Tip-Top.

The Manual addresses the issue with an element of FEAR!
Don't!
Never!
On my God ... if you do ... you'll be so sorry.

Baloney.
Get those Pilot Screw Anti-Tamper Plugs out-of-there!
Have full Fine Tuning ability.

Just be very careful doing the drilling and extraction of the Plug.
They work so much better having the un-chopped-up slot for the screwdriver to manipulate them for Fine Tuning.

I can't remember where I saw them ... but there was a source selling the Pilot Mixture Screws with extensions having a knurled top-end that you could actually tweak by hand.

I don't know if they came in the sizes that would work for the 650's and 750's ... but, it sure make life alot easier on all of us to be able to just reach-in and tweak the Pilot Mixtures by hand!