Xs650 Bobber

[Ccatt42]

alright guys so i picked up a bike a few weeks ago that was stock, turned it into a bobber and now im focusing on the engine. Im running pod filters and open pipes. i know i need to rejet my carbs, (does anyone have any idea what jets i need to order?) Im having a couple of problems right now, the clutch pushrod seal, which is fine i will have no issues replacing. And the i am having a carb issue asside from the jets. when i get the bike moving it bogs way down at higher rpms. so id assume im running super lean. at some point today i will be taking the carbs off and checking for air leaks. and with my carb jets i will be running it somewhat hard, mostly higher rpms. thanks for any feedback guys.

 

[angus67]

what year? what carbs?

 

[Ccatt42]

79' mikuni 38s

 

[Ccatt42]

Ive noticed i have one head pipe burning super hot compared to the other one. So im assuming i need to re sync the carbs or i jave a float sticking...

 

[retiredgentleman]

Don't assume anything. Carbs are a precision device that require a detailed inspection to see what you are working with.Have you read the "Carb Guide" that is in the Tech section? Its wise to not run your bike anymore until you have read the guide, and taken the carbs apart to verify what jets/float levels you have.

 

[Ccatt42]

I dont drive it, just start it for like 2-3 minutes every couple days

 

[retiredgentleman]

When I said, " Its wise to not run your bike anymore until you have read the guide, and taken the carbs apart to verify what jets/float levels you have." ......I mean do not run the engine anymore.

If you report what jet sizes you have now, then you will get advice on what you require.

 

[Ccatt42]

Alright. Thanks for the advise i wont run it till i get time to pull the carbs

 

[Ccatt42]

Another thing i noticed is it is an extreme dog at higher rpms. Anything over half throttle. I still havent gotten a chance to get the carbs off, just got hurt st work this past week, so i gotta take r easy. Just want some more knowlege before i rip her apart more.

 

[Ccatt42]

Alright so i took the carb apart, put a 140 main in, will probably go back down to a 137.5. The problem im having is its running super rich. Its exhaling black soot from the exhaust, and im still having the same problem, my left cylinder is running super hot, and my right cylinder i can touch the exhaust after its been on for a few minutes, so i will check that plugs gap tomorrow, i have an electronic ignition so i doubt a coil is out, because im almost positive they run off the same coil

 

[650Skull]

Wasting time........................

Adjust timing chain,
Set the tappets,
Static time the bike.
Clean all connections, couplings and make sure all grounds/earth connects are clean and making good contact,
Continuity test all wires and check for any nicks or damage
Disassemble handle bar switches and make sure all connections are clean, reassemble,
Make sure the Battery is fully charged, load test if necessary, if losing any charge buy a new one.
Check spark at the plugs. If spark is better on one side then swap leads and see if the problem follows. If not check coil/condensers/leads/caps and replce if necessary.

Your problems could be electrical as well

Do not assume. Changing a main jet alone is wasting time.

Read the carb Guide, per RG request
Remove carbs and clean..................... lots of threads on passageways that need cleaning.............do some reading in the Tech menu.

Check float needle and o-ring,
Check float height

Procedure is required............Do not assume it is one thing tha is the problem.

 

[retiredgentleman]

Your cold cylinder may be as simple as a bad spark plug or bad spark plug lead or a high resistance cap.
Black smoke from the exhaust may mean the head cylinder gasket is passing oil into the cylinder(s).
I think its obvious why the PO sold the bike.....................its need a lot of work.

You're doing the same as a lot of lads do. You buy a used bike (condition unknown), change the look of the bike, install pods and open bikes, and then wonder why it runs like crap. You would have been better to leave the stock air box/filter and stock exhaust in place, while you drive and get familiar with the engine/bike. Over the first 6 months to a year you would have found out what the main problems are, while running in a stock configuration. Only after sorting out the problems, left from years of neglect/abuse, would you then change to the pods and open exhaust, that are so highly sought after.

You likely have multiple things that need repair/replacement. Its a step by step process. I suspect you will be doing a top end re-build before long.

 

[weekendrider]

Ccatt42 I suspect your left cylinder is fine. The right not firing at all. That is the reason you can touch it.

 

[fredintoon]

Hi Ccatt,
Betcha your "cold" cylinder ain't running at all and a 326.5 cc single will for sure "bog down", eh?
Best you clean the carbs again.
Properly.
Completely apart (except for the butterflys, they are a bitch to remove & replace)
Poke a guitar string through each jet.
Blast carb cleaner through every passage.
Don't forget the enrichening circuit.
Ultrasonic clean the bodies.
But first, check if whatever EPA-mandated adjustment blocks were installed on your carbs have been removed.
Then check that whatever aftermarket ignition has replaced the bikes points etc is working properly.

 

[weekendrider]

Or like RG suggested it could be a bad/fouled plug not firing the gas that is being delivered.

 

[Ccatt42]

Half of the parts were missing, and it didnt run when i got it, i paid 150 for it, then i conpletely stripped the wire harness, welded up the frame, and am slowly making progress, ill lash the valves later today, and swap out the spark plugs, i know a majority of the problens are stemming from the carb set up/ exhaust / intake, i have a muffler on it, but its not quite as much back pressure that id like to have. When i get home to do ill be swaping the pilots and such. Floats are at the correct hight. To oem spec. I kbow its running rich now, so like i said ill switch to 137.5 mains. Maybe even 135. I truely dont think the problem will stem from the ignition coils., could very well be bad leads or plugs.

 

[5twins]

With near open pipes and pod filters, your '79 carb set will need probably 140 or 142.5 mains. But, with those you must lean the needles a step. If you haven't, that could be partly responsible for the black plugs. Also, if you are starting the bike using the choke, that will blacken your plugs right up and give a false plug reading. It takes a good little ride of maybe 5 to 10 miles to burn them clean again, and you're not doing that.

For tuning purposes, you should probably get a couple sets of plugs. Start the bike with one set and warm it up. Then shut it down, swap in the clean set of plugs, and re-start without using the choke.