No High RPMS after First Start - then OK.

jimdi · 650Rider Supporter Joined: Oct 27, 2005 Posts: 512

1981 Heritage Special
Ok - New Problem - It starts - but sputters and has no RPMS above 2,000 -
will run like that for 1-5 minutes - then presto! It runs fine.
(oh and once in a while I get the mystery Dies while running - which sucks going around a corner)

I have -
Replaced Coil, wires, plugs, boots.
I have pulled and Cleaned the carbs and double checked float levels.
I have even pulled the plugs out of the Idle mixture screws and set them from 1.5 to 2.5 (richer)

I have also installed a fuel filter.

Help
Jim

treecutter

Check that the choke passeges in the float bowl are clear, I missed these the first time I cleaned my carbs as well, similar symptoms.

jimdi · 650Rider Supporter Joined: Oct 27, 2005 Posts: 512

In the float bowl - I cleaned (blew out with carb cleaner & tube) the 2 small openings near the gasket, as well as the small tube that hangs down and intersects the bottom of the bowl. Also cleaned the passage in the bowl.
Are any of those the Choke passage?

Any help appreciated.

y next step is to pull the idle mixture screws and blow out those passages with carb cleaner.

jimdi · 650Rider Supporter Joined: Oct 27, 2005 Posts: 512

Cleaned out Idle mixture screws & passages - O rings ok -
Changed plugs -

Still rought idle for 2 minutes then fine - even after bike warmed up.

HELP!

Jim

kingwj

Check the points for gap and retime the bike. As a British car owner I have learned that 95% of carburator problems are electrical. My XS behaved much better after I got the points spot on.

I am a bit confused by your last statement. The idle is rough when you start the bike either cold or warm? Do you still have the 2000 rpm redline?

jimdi · 650Rider Supporter Joined: Oct 27, 2005 Posts: 512

The bike is rough after first start - no high end just rough idle 2k top end - cold or hot - if it's sat for about 30 minutes.
It has TCI igniton and the timing is dead on.
(no points - electronic)

I took the carbs completely down - cleaned every part, every jet - inspectied the diaphrams, set everything to factory spec and it still doing it - but now it seems less often.

When it kicks in and runs great- it is just as if someone has thrown a switch.

Did it again this morning and I took the idle mixture down to 1.75 turns. (leaner)

Since my plugs looked a little Ashy (rich) I thought this might help.

Still looking for ideas

I hate intermittent problems!

Thanks
Jim Question

jimdi · 650Rider Supporter Joined: Oct 27, 2005 Posts: 512

Turned out to be two problems -
iffy solder joints in TCI box circuit board (resoldered) and on the harness connections - see my article in the News section and this:

Breather info: I was going crazy with my mixture settings...
I have a 81 xs650 H special with Mikumi 34 stock carbs.
Factors is the breather goes from the heads to a T then into each of the air boxs on the carbs - with 2 vents shooting the oil fumes right into the carbs.

No matter what I tried - my plugs would foul. And idle was erratic.

I rebuilt the carbs.
Factory mix had the screws at 2 out - but it liked to be LEANER - about 1 turn out - even then my plugs were getting all carboned up!

Then I pulled the breather out of the carb box - plugged the stock air box openings for the breather (so dirty air wouldn't bypass the filters)- and put an automotive breather on the breather hose! (keeping it OUT of the carb air box)

What a difference - idles smoother - and the mix is back to 2 out. Peformance went up too!

Turns out the Oil fumes - from the breather were richening up my mixture with the factory set-up and fouling the plugs.

Getting the breather out on it's own - away from carb intakes made a huge difference!

Jim

Problem seems solved.

What Happened to 650rider.com?

Yamaha xs650