FJ600 question on speeds

Hi all ,
I have got an 1985 600 since last month, I was told carbs were cleaned , spark plugs at right distance, oil changed.
I rode it home at around 100-110 kph (68 mph) no problem as I was getting used to the classic bike...

Now few weeks later I tried to go a bit faster on a stretch of highway however in 6th gear it didn't go over 80 mph??! I tried one gear down from a lower speed and then ot seemed to keep reving upwards pretty sure it was over 80 mph then but had to brake and leave highway.

I was under the impression that I could rev easily up to upper end revs but it's not like that , does it aound to you guys as normal for this bike or should it been easier even in 6th gear ? As I had a BMW F650!single it's a hard comparison (injection bike rev limited yet easily pulling to
over 90 mph
Txs
Richard

 

It should easily top that, what revs was it pulling in top at 80mph and what gearing is it running?

Are you sure it's not getting clutch slip? revs increasing but not speed?

I'd expect to get something like an indicated 120 mph out of a good one

 

Thanks, I am sure that when I was in 6th revs and speed were plain constant at full throttle, does not look like clutch slip at all just hard to do 8000 and up revs, I recall at lower speeds lower gears revving up is a bit easy .
I need to do some dedicated test runs now and generate more precise numbers for this question I guess , is there something obvious to check , like number of teeth on the cogs and such or could a carb cause pulling issues at higher speed?

Just remember an important detail , it had an open pipe and I added dBkiller and packed the last 20 cm of the exhaust, can there be extra backpressurr holding it back??

 

I'd suspect clogged holes in the emulsion tubes.
Nevever believe what you were told by a seller without confirming the work yourself.

 

It's easy to take it out and try it

 

how is your chain ? well oiled?`

 

Compression check ?

 

How does your exhaust taste? lick the muffler... DOO IT.


I just wanted to ask a random question!

 

THAT'S WHAT SHE SAID!

 

+1.Eliminate future headaches by learning your bike.

Gary H.

 

My first though is always, "yeah, rrriiiiggghhhttt" when a seller says that.

There's only a few few people that I would actually believe that from.....and the majority of the select few are right here.......

 

OK, I took the fill material back out of the exhaust just leaving the dB-killer in, immediately noted more noise at idle again but took the bike for a ride this weekend, there are no issues revving up way over 6000 now even in 6th gear so problem solved. Does this make sense ? that the exhaust packing was creating to much backpressure when asking higher power from the engine, given that normally this bike had a left and right exhaust and min eonly has 1 it may all have added up to a too restricted situation, the noise is OK ish now , with earplugs and >3000 rpm the bad resonance noise is not there so I'll leave it like this now.

 

Very possible. These bikes are a very free-blowing bike. Very little back pressure, if any, to begin with.