[Daisydog]

Hello everyone , proud new owner of 748 sps however there is a fault with it ! I knew when I bought , bike starts and runs fine and revs up fine at a standstill , but when under load will not go past 70mph ? I haven't witnessed this first hand as only just collected and ridden up and down road where it seems fine .
Any ideas anyone ? Any help gratefully received cheers

 

[Shazaam!]

Dirty air filter. Dirty fuel filter.

 

[Daisydog]

Will try those items be great if it was something as simple as that cheers ! Previous owner tried ht leads and plugs and coil , engine sounds good so hopefully no trouble there

 

[Joeii]

Possibly the clutch is rather worn and is slipping?

 

[Daisydog]

Another thing to try ! Thanks for advice passed mot today so got to tax and put on insurance and will post how it rides , thanks everyone for reading post any tips welcome

 

[pat1098]

I would definitely do the fuel filter first.

Fixed a few of these with those exact symptoms. They are an item which is meant to be replaced every 20,000 kms (12,000 mi) and is often missed, as it can be a hassle.

But of course it may only take one fill of contaminated fuel to block it up..

There are a few tricks to this job if you are doing it yourself.

You should replace the large green O-ring around the tank flange as well, as they are not really reusable (tend to grow after long contact with unleaded fuel).

And use longer 5mm bolts to pull the flange back into place.

Also pay close attention to the large plastic nut which retains the wiring, as these fail when they are old. Non-standard metal replacements are available.

 

[Daisydog]

Cheers pat 1098 , going to change all filters , belts etc but some good tips there . It sounds great lets hope I can get it running sweet .

 

[Tchase]

When I had this problem on my mazda (yah I know its nota bike) it was out of time. Ran fine idle, ran fine revving, but under load ran like shit.

 

[1fast750ss]

Typically when under a load, the clutch when worn out, will slip, not allowing the power to get to the rear wheel.

Check your other items too, as they are simple to get at, however check your clutch plates, as they may be worn out pretty bad. If the stack height is under 38mm, they are probably in need of a change.

 

[Daisydog]

A mate did say if it's one tooth out on the belts may cause this, car or bike principal is the same !! Cheers for tip ! Cheers tchase

 

[Daisydog]

Thanks for that 1fast750ss , are plates fairly easy to change ?

 

[pat1098]

Just do the fuel filter first is my tip. Other issues like the clutch can be easily accessed once you have sorted the running problem.
The fuel filter has probably never been changed, as they are a PITA to access.
Drain the tank (drain plug under rear RHS) and place it on clean cloths on the bench, up side down, to access the fuel pump flange.
With the pump and flange removed, the filter is easy to change. You might need to replace a one-use hose clamp or two with the screw type.

 

[1fast750ss]

The plates are very easy to access. Clutch cover is 4 bolts, then the 6 pressure plate springs. Pull the pressure plate off, "noting the arrow on the plate to the slot on the hub post, as they must match". You can take the plates off one at a time, then stack them on the ground as you pull them out. This way you can reverse to install. When they are all out, measure the height in mm's.

Should be at least 38.5mm. If under 38mm, they're done.

Pat is correct with the fuel filter, as if it's not been changed, you'll have idle issues all the up to WOT.

 

[Daisydog]

Thanks for advice and tips will let u know how I get on

 

[martinc]

Battled similar problem for a year...turned out to be the fuel pressure regulator.

 

[Daisydog]

Interesting , another avenue to follow up , what did we do before the internet !!, cheers

 

[1fast750ss]

Interesting , another avenue to follow up , what did we do before the internet !!, cheers

Rode our bikes and looked at Playboy magazines.

 

[Daisydog]

When I changed fuel filter , breather pipes in tank were blocked solid ,cleaned them out and it's flying ! Changed oil and filter , air filters and timing belts it runs really good now sounds great . Thanks for help , suspension service next I think been neglected , how can u not look after a 748 sps should be locked up !!!