Intro and bike

K

krob

XS650 Enthusiast
Messages
59
Reaction score
15
Points
8
Location
Wyoming
Hi all, let me start by saying this site is awesome. I recently purchased a 1979 xs650 special. Unsure whats going to happen with her yet, but I am pretty excited about this little bike. THanks for all the usefull info you guys provide on this site!! Pictures of the bike soon!!:thumbsup::thumbsup:
 
krob said:
Hi all, let me start by saying this site is awesome. I recently purchased a 1979 xs650 special. Unsure whats going to happen with her yet, but I am pretty excited about this little bike. THanks for all the usefull info you guys provide on this site!! Pictures of the bike soon!!:thumbsup::thumbsup:
Click to expand...

Hi krob and welcome,
we eagerly await the photos.
If it's fit to ride, do yourself a favour and just ride it for a season before deciding to do stuff to it that can't be reversed.
 
Pretty rad old bike. I haven't seen to many with this king and queen seat...looks to be a stock seat. Not 100% on that though. I plan on just getting it tuned up to ride for now. It runs and rides pretty well but it needs a few things for sure.

First thing was to clean and rebuild the carbs. They should be back on the bike tonight. I got new oil filters from mikexs so I can give her a good oil change. Also got an old style petcock. I have had issues with the vacuum style before on another bike, and I know they can work if they are set up right but I don't want to deal with the complexness of them, so they are gone. I only ordered one intake line cap thinking there was one with the petcock :doh: I guess duct tape will have to work for now. :wtf:

One thing that I don't like on these carbs is the fuel delivery. I think the 4 ports is a bit overkill but I could be wrong? Can I just eliminate the top ports and run a T between the bottom two ports? Or is there a reason for the way it is set up? Does anyone make a piece that will fit in there? I went to the local hardware store and couldn't find any tubing that would work. Its not a huge deal but it would just simplify things a bit.
 

Attachments

  • stock 1.jpg
    stock 1.jpg
    51.5 KB · Views: 365
  • Stock 2.jpg
    Stock 2.jpg
    63.1 KB · Views: 355
  • Stock 3.jpg
    Stock 3.jpg
    58.5 KB · Views: 347
Hi krob,
ooh! Shiny! I'm not in favour of those stock pullback bars but try 'em for a while to see if YOU like them.
Same deal with that KQHB seat.
Mind you, although there's just about a zero market for the pullbacks there's an Australian list member absolutely desperate to find a seat like that KQHB of yours if it ain't to your taste.
And if your carbs are the one's I'm thinking of those two top fuel inlets ain't fuel inlets, they are breathers.
The local hardware store is unlikely to stock fuel grade tubing and even if they did have tubing the right size it'd most likely be "food grade" as used in aquariums.
Best you go to a motorcycle or small engine shop and ask them for Tygon fuel hose.
 
There are 4 fuel ports on the carb. The two uppers are supplied with gas from the separate petcocks and the and the bottom two are connected together with fuel line. I'm sure they couldn't be breather tubes, or gas would spill out of them all of the time.
 
fredintoon said:
Hi krob,
ooh! Shiny! I'm not in favour of those stock pullback bars but try 'em for a while to see if YOU like them.
Same deal with that KQHB seat.
Mind you, although there's just about a zero market for the pullbacks there's an Australian list member absolutely desperate to find a seat like that KQHB of yours if it ain't to your taste.
And if your carbs are the one's I'm thinking of those two top fuel inlets ain't fuel inlets, they are breathers.
The local hardware store is unlikely to stock fuel grade tubing and even if they did have tubing the right size it'd most likely be "food grade" as used in aquariums.
Best you go to a motorcycle or small engine shop and ask them for Tygon fuel hose.
Click to expand...

So the seat is a KQHB? Good to know. I will most likely use that seat for this season unless someone wants to trade another seat that is of interest to me. I would imagine by the time a guy from Australia put shipping into two seats it would be cheaper to buy something else that is similar.
 
The bottom fuel hose is a crossover. It balances fuel delivery between the carbs in case one petcock starts running dry once fuel levels in the tank drop below the hump in the center. I wouldn't change anything around there. It was designed to do a certain something a certain way and I doubt you'll improve on that.

You can get vacuum nipple caps at the local auto parts store. This 7/32" size fits perfectly. Clamp them on some how, even if it's just a little spring clip like used on the fuel lines. They'll pop off if you don't if you get a backfire. And yes, that can and does happen, even in a good state of tune. This is an old, rude and crude engine design, a little rough around the edges, lol .....

VacCaps.jpg
 
THanks 5twins. I get what the crossover piece is for. I am going to run a single petcock anyway. I was hoping there was a piece that was a T that you could replace the crossover with, so I could run one fuel line from the petcock to that T that replaces the crossover instead of having to go from petcock to a T to the upper fuel ports. I also would then have to shut off the upper fuel ports somehow, but in the future it would be easier to take off the one fuel line instead of two.
 
Carbs are ready to go back on the bike. Hopefully I will have time tomorrow. They turned out pretty nice with a bit of work.
 

Attachments

  • Carbs cleaned.jpg
    Carbs cleaned.jpg
    124.3 KB · Views: 332
krob said:
There are 4 fuel ports on the carb. The two uppers are supplied with gas from the separate petcocks and the and the bottom two are connected together with fuel line. I'm sure they couldn't be breather tubes, or gas would spill out of them all of the time.
Click to expand...

Hi krob,
sorry if I misled you, I've seen posts about some early XS650 carbs having vent lines that were confused with fuel lines but not on yours, eh?
And KQHB is an initialization for King/Queen/High Back. Every aftermarket seat manufacturer makes them for the Chopper guys and Yamaha made them as an option, too.
From the photos, yours looks like an aftermarket seat, as I remember the stock KQHB seat on my own (long gone) '79 Special, it's hump was far less extreme.
After I modified it by sawing it's tail off (stupid me, not realizing that seat's rarity and consequent high resale value) and replacing the torn original with a Saddlemens cover it looked just like a stock Special seat.
 
fredintoon said:
Hi krob,
sorry if I misled you, I've seen posts about some early XS650 carbs having vent lines that were confused with fuel lines but not on yours, eh?
And KQHB is an initialization for King/Queen/High Back. Every aftermarket seat manufacturer makes them for the Chopper guys and Yamaha made them as an option, too.
From the photos, yours looks like an aftermarket seat, as I remember the stock KQHB seat on my own (long gone) '79 Special, it's hump was far less extreme.
After I modified it by sawing it's tail off (stupid me, not realizing that seat's rarity and consequent high resale value) and replacing the torn original with a Saddlemens cover it looked just like a stock Special seat.
Click to expand...

KGHB...never knew that acronym. Good to know haha

Ya I will eventually change the seat but it will be one of the last things. If someone really wanted it I suppose I would trade it for something that is of equal condition.:thumbsup:
 
Thanks Skull that is a very useful site. It has already been great help for me. It is sometime difficult to sift through the clutter on forums to find a needed answer, so it is really nice to have it all organized in one spot.

I am having issues with my carbs though, and was hoping somebody could help. I have taken them apart and cleaned them as through as I can, and replaced necessary parts.

I set the mixture screw to 2.25 turns, and will adjust depending. I upped the main jet to a 140 and the pilot to a 30, because I plan on using the foam pods filters and straight flow exhaust. I havent adjusted the needle yet, but will do so if i need to after testing.

My problem is I cant get the engine to idle without turning in the throttle adjustment screw. Its not much of a turn at all, I would say 1/2 to 3/4 of a turn after it has had contact with the lever mechanism. Is this normal? If not what could be causing the issue? My guess would be a dirty pilot circuit but I am almost certain it is clean. Just wondering if this is a normal issue before I take my carbs apart to reclean. I was hoping to ride it once before tearing it apart to make adjustments on the carb.

One other quick not I did not have air filters on the carbs when I was having this problem.
 
Hi krob,
if I correctly understand your post, don't worry. That's how they are supposed to work.
Completely shut off ANY carb and the motor will stop.
The adjustment screw is there to hold the carb that little bit open so the motor will idle rather than stop.
It's a balancing act between the adjustment screw, the choke setting, the idle screw setting, the ambient temperature and the engine temperature.
 

Similar threads

DB90
These things just keep multiplying!!! 🤤
Replies
11
Views
373
DB90
DB90
S
Buying a 1978 xs650 on Tuesday. Need guidance!
2
Replies
24
Views
1K
650Skull
650Skull
cmyoch
Well, I may be back!
Replies
0
Views
68
cmyoch
cmyoch
DB90
1981 Chopper Build
Replies
2
Views
373
DB90
DB90
ssjody
1981 XS650 Special - Build Thread
4 5 6
Replies
114
Views
5K
ssjody
ssjody
Back
Top