Vfr750 flat spot

Craig1017

Registered User
#1
Hi I’ve posted this in the technical section before realising there was a dedicated section for the older VFRs. I’ve recently purchased a 1997 VFR750 which is in great standard condition and has covered about 20k miles. It runs very well apart from a hesitation at 6500rpm which lasts through to about 7000rpm after which it runs fine again. It’s quite pronounced and almost feels as if it’s dropping onto 2 or 3 cylinders. It’s only apparent when riding. When stationary it revs throughout fine. Is this something that anyone has come across before?
 

50th VFR

Registered User
Site Sponsor
#2
Spark plug failing under load is one thought.

Second is fuel residue contamination in carbs if bike was sat for prolonged period with fuel in carbs.
 

Sye

V-Twin and V4 Aficionado
Site Sponsor
#3
What 50th VFR says plus check the small sub filter next to the airbox hasn't fallen to bits.
 

Craig1017

Registered User
#4
Just a quick update, the main air filter looks very old so new one on order. The sub filter was present however it had turned to a paste lick consistency so that’s been replaced. Hopefully this will help.
 

Craig1017

Registered User
#5
Further update. I’ve serviced the bike and replaced plugs, filters etc including the small extra air filter. After a road test my initial thought of a flat spot were obviously wrong......it starts to almost misfire/ feel hesitant from 6500rpm all the way to the redline. It pulls through it but it’s definitely not happy. Up to 6500 it’s absolutely fine. I’m thinking maybe coils or cdi breaking down at higher revs or is still more likely to carburation?
 
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