carb jet numbers!! help!

Hello all.

Awhile ago I put pods on the bike, and the bike was tuned professionally. Now I want to put the bike back to original, but I am sure the mechanic did not put different jets in the carbies. He did not give me any “old ones” nor do I recall him telling me he ordered new ones. The jets in the carbies are old, judging by condition and screw marks. So I am trying to establish what I have before I go ahead and unscrew the pilot to lean up the mix on all carbies, as I am assuming this is all he did to richen the mixture with the pods on.

I have looked everywhere for details, even the older posts, trying to find info on the below numbers. I found the details about jetting in the old posts very interesting, but little use to me, because the bikes are North American? The manuals I have come across do not cover at all the details I might need. I have not found one that covers my carbs either. They are Hitachi, an CV type.

The bike is now stock all round, stock exhaust, stock air filter. 1982 XJ650 Australian version.

The needle is a Y10 (no clip positions)
There are two jets under the jet cover inside the top of the carby, one is stamped 50, the other stamped 205.

In the actual float bowl, there are two jets, one stamped 112, the other stamped 43.

On the top, exterior, there is a rubber grommet, beneath which there is a screw. Each carby has this also. This I believe is the pilot screw.

Am I right in thinking all I have to do is lean the pilot screw half a turn at a time? Are the center cylinders meant to be richer?

Cheers for the help!

 

black stock, the screw you mention, under the grommets is an Idle Air Screw(Affects mixture)

Clockwise(IN) Leans out the mixture
Counter Clockwise(Out) richens the mixture

I dont know 650s(amer) much less the australian 650,, but a pilot jet of 43 and a main jetof 112 sounds right for the UK Version

Air jets sound correct. The needle should be a Y-11 for the UK jet needle.

How is the bike running currently? How much have you played with the Idle air screws?(the one under the grommet)

PS the US 650(non turbo) ran a main jet of 110, pilot jet of 40, jet needle of y-10.
Air jets, the same size you mentioned prior, were identical to whats on your scooter

 

g'day.

well it is making a bit more sense, but does the idle mixture screw affect the bikes mixture throughout the rev range?

if i put the stock intake system back in, i will need to lean out the mixture, can i do that via this screw?

cheers.

 

This is what is on my XJ650Rj stock.
So your fuel jets are bigger them mine, if you took off the header and pods went back to stock, you are correct thinking you'll need to lean it out.
The pilot screws will adjust your low end below 3-3.5K.
Do some plug chops to see were you are now.

 

Hi Guys,
I've got an '81 XJ 650J that I bought over the summer. It wasn't firing on #4 so I tore the carbs down myself. I'm not a mechanic but I might be able to play one on TV. :O)

What I found was rust in the carbs. No varnish etc but I did soak them and clean them anyway. The rust was stopped at the inlet screen at the inlet. Thank God for the screen. She was totally packed at #4 and not letting fuel in fast enough.

I kept all the parts separated so that #1 got it's original parts back #2, #3 #4 etc. When I started putting them back together I discovered the Air jets were somewhat different. The larger jet was the same in all 4, a 206 (stamped on top). The smaller one was a 60 on #1 and #2, but a 50 on #3 and #4. Was this normal or has someone been tinkering?

I can't make a good comparison. Obviously it is running so much better I've got no benchmark. I guess if it's running good let it alone????

Sean

 

Snoopy, someone's been tinkering, and bad.......the correct specs for stock 1981 XJ650H carbs are:

Main FUEL jets: #110
Pilot FUEL jets: #40
Main AIR jets: #50
Pilot AIR jets: #195
Main jet NEEDLE: Y-10
Air compensator jets: #36

However, I note that you describe your bike as an XJ650J model.....the J is the year code suffix, and indicates a 1982 model:

http://www.xjbikes.com/Forums/viewtopic/t=14577.html


The correct carb specs for a 1982 model XJ650 Maxim are:

Main FUEL jets: #110
Pilot FUEL jets: #40
Main AIR jets: #50
Pilot AIR jets: #205
Main jet NEEDLE: Y-10
Air compensator jets: #36



By the way, the #206 that you are seeing is really probably a "205", as they are sometimes hard to read.........and, I have never seen nor heard of a #60 sized air jet, I don't think they existed, at all, on any Hitachi carb.

I would first figure you what year bike (and engine, as they may be different if a transplant was involved) that you have, and then jet the carbs correctly and accordingly.......I assume that the intake and the exhaust systems are stock?

 

Thanks Chacal,
I agree the 206 easily could be 205 and probably is. The 60 and 50 are stamped very plain though. No mistake on them.

I'll recheck the year and model. I came up the J model from the Haynes book I purchased. I matched the serial number from the frame and it told me 1981 XJ 650J. I'll check that again tonite and verify it for you.

As far as I know all is stock. The headers are for sure and the pipes are stock except someone knocked the baffles out of them (I assume) to make it louder? I'm looking for some stock pipes used. But I have a few other things that top the priority list on my tight budget.

I wondered if the Carbs had been cannibalized from another bike. Did Yamaha stamp the number of the carbs, #1, #2, #3, #4 on the bottom of the float bowls? I noticed there were numbers under mine. I have 2 that have a #3 and 2 that have a #2 stamped on them. That made me wonder if they weren't original.

I'll let you know about the year/model when I get home. Far as I know all is supposed to be stock/standard........but it's early 80's and I have no idea how many folks or even who owned this bugger over the years.

I bought it for nothing off a guy who was living in a hotel room. He had been riding it as his sole form of transportation and his job we requiring him to have a car. He wanted to get rid of it fast.

Sean

 

The carb bowls may be marked with some inked figures, but the carb bodies are SOMETIMES marked #1, #2, #, and #4, which indicates their relative position in the rack (#1 being the far left, #4 the far right). One way or another, you're going to have one of each carb body, since each body is slightly different from the others (actually, the #2 and #3 raw carb bodies are the same, but once they're dressed with all their accessory peices, then the #2 and #3 are different completed units, too).

 

Hi Chacal,
Just got home and checked my serial. I'm a little confused but maybe it's a date thing.

The frame number is JVA5N800 . The date of manufacture is stamped as 9/81. Were they making 82 models fall of 81? I know car makers do that. Does Yamaha as well? According to my book, the 5N8 denotes J model from 82. But the date stamp says 9/81.

Sean

 

Hey Sean.........yes, your model is a 1982 XJ650 Maxim, built in 9/81. Just as with auto manufacturer, motorcycle mfgs. also played that same game...........

A build date of 9/81 puts you well into the 1982 model year.

 

sorry for the bump on an old post, but i have a similar question.

I just set the float level and cleaned the carbs on my 81 xj750

I'm looking down into the carb throat from the top at the main and pilot air jets, with the screw that retains the plate above them closest to me.

Which is which? manual says main on "top"/ closest to the engine (with rack on bike), and pilot on the bottom, or closest to airbox.

main air jet size 80
pilot air jet size 225

the picture from the manual, however, shows a larger size opening in the jet closest to the engine, which confused me.



SOOO the question: is the correct configuration for the air jets, starting closest to the AIRBOX, 225 then 80? pilot then main?

i might have figured out why my bike wouldn't start. =D

 

The PILOT air jet (#225) goes directly above the PILOT fuel jet (thus FORWARD in the carb body).

The MAIN air jet (#80) goes above the MAIN fuel jet (thus the CENTER position in the carb body).

The REAR position is where the cover plate hold-down screw goes, if that carb was equipped with the cover plate (not all models were).

 

awesome thx. the pictures/captions in the haynes manual say the main jet is forward, but when you actually look at the size of the hole in the picture it looks like the pilot (225) air jet is forward as it should be. thanks for clearing that up chacal.