Strange Problem

[dan7uk]

While riding, when I release the throttle and pull in the clutch to shift, the bike keeps a fast rpm for a couple of seconds before dropping to normal.  Does this when going thru the gears, up shifting or down shifting.
I adjusted the throttle free play and it had no effect.  Any suggestions?

[98valk]

idle mixture screws or and mostly there is a vacuum link. PAIRS valve vacuum hoses or the normally intake manifold unused vacuum port caps are leaking.

http://www.factorypro.com/tech/tech_tuning_procedures/tuning_carbtune,CV,lower_rpm_engines.html

[h13man]

I'd say a vacuum leak. I'd replace all lines as they are 30'ish years old and depending on care/storage in its previous life.

[Mooskee]

+1 on most likely a vacuum leak.

[WintrSol]

Also +1 on vacuum leak. Lean engines tend to 'throttle hang', and when the vacuum spikes, even a tiny leak will contribute to this. You can test this without moving; raise rpm to about 3k and quickly close the throttle. It should quickly return to idle, if not, it is too lean. If it drops lower than comes back, too rich, but it doesn't sound like the problem here.

[dan7uk]

This bike is a 99 interstate and I picked it up about two months ago.  I'm sure the bike hasn't been desmog in its 26 years.  Seems everyone who posted is in agreement on a vacuum leak.  I owned a 99 standard Valkyrie about 15 years ago and I put a desmog kit in it just for precaution.  I guess I will be putting one in my current one.
Thanks for all who posted, I never thought of a vacuum leak could be causing my problem, are the red eye desmog kits still available?  Have a link?

[98valk]

This bike is a 99 interstate and I picked it up about two months ago.  I'm sure the bike hasn't been desmog in its 26 years.  Seems everyone who posted is in agreement on a vacuum leak.  I owned a 99 standard Valkyrie about 15 years ago and I put a desmog kit in it just for precaution.  I guess I will be putting one in my current one.
Thanks for all who posted, I never thought of a vacuum leak could be causing my problem, are the red eye desmog kits still available?  Have a link?

see my post how I did the desmog. first time I did the heads were on the engine. this was a set of ported heads so I did them before I installed the heads.

https://www.valkyrieforum.com/bbs/index.php/topic,105991.0.html

[dan7uk]

98 Valk, I looked at your attachment didn't see anything about desog just work on your heads.

[SCain]

This bike is a 99 interstate and I picked it up about two months ago.  I'm sure the bike hasn't been desmog in its 26 years.  Seems everyone who posted is in agreement on a vacuum leak.  I owned a 99 standard Valkyrie about 15 years ago and I put a desmog kit in it just for precaution.  I guess I will be putting one in my current one.
Thanks for all who posted, I never thought of a vacuum leak could be causing my problem, are the red eye desmog kits still available?  Have a link?

Look at the signature line for Mooskee, he is a VRCC vendor, sells a De-Smog kit on his web site.