Full throttle, bogs down...

[bikerjack]

I have a 1979 XS650 Special. Stock everything, except 2 into 1 short pipes going down right side. Even has stock airbox and side covers. Starts good, runs good. Full throttle, she bogs down and actually slows down, especially on highway at 65 mph. Thats when I have to throttle back for it to catch up. Also, once she warms up, very high/fast idle. Any help would be nice....

 

[retiredgentleman]

You need to remove the carb float bowls, and remove the main and pilot jets, so that you know what you are working with. The "Tech" section here has the "Carb Guide", which will tell you what is stock, and you can compare to what you have.

Also, you should remove the carb diaphrams and check that there are no holes in them.

 

[bikerjack]

ok, thanks retiredgentleman. appreciate the advice.
also, went out and revved the motor while it was sitting on the centerstand. noticed it was buzzy on the highway but man!!! it was vibrating worse than my harley and scooted backwards on the centerstand itself. carbs will be coming off in the very near future.

 

[retiredgentleman]

ok, thanks retiredgentleman. appreciate the advice.
also, went out and revved the motor while it was sitting on the centerstand. noticed it was buzzy on the highway but man!!! it was vibrating worse than my harley and scooted backwards on the centerstand itself. carbs will be coming off in the very near future.

Yup, that vibration is normal. This was one of the first bikes to have a low speed reverse motion feature. Very useful for moving the bike in the garage

It seems some years seem to have more vibration than others. My friend has an 1980 XS650 and the vibration tore his licence plate into two pieces. Yet, my 1978 XS650 has no vibration at the licence plate.

 

[DirtyErnie]

Sounds like your pilots are lean because of the open exhaust (hanging idle). My experience with the 2-into-1 is that the stock needles become waaay too rich because of the vacuum signal produced by the exhaust. If you change to the BS34 carbs from an 80-84 model you can use the Xs Performance/Keihin needle kit. Maybe you can set your needles down to the leanest setting and get close...

 

[bikerjack]

thank you, dirty ernie. i would like to keep the 38's i currently have on my xs. just wondering what i can do to them to get the bike running as great as i know it can run.

 

[Tron]

you will need to up the pilots and mains.. maybe 2 up on the mains and one on the pilots to start..

the vibration is normal but can be minimized by properly synced carbs and having the timing dialed.

 

[bikerjack]

and there we have it....thanks, tron

 

[Tron]

Also while your there, double check the float height. Should be 24mm from the gasket surface.

How short is the 2-1? you may just need to go one up on both jets.