SFC 1000 - engine starts to behave strangely

Beucars

Beucars

Hero member
Location
Central Europe
Hi everyone, I'm seeking for your technical expertise:

I've a question about a 1000 RGS/SFC which is very regularly maintained and ridden for the last 4 years.

When I was waiting for a traffic light last Saturday a small sound (like a small bird) could be heard from inside the fairing. The sound follows the rotation sequence of the engine and you could only hear it at stationary revs. First, I thought about a dry revmeter cable or so.

After inspection at home, I had the feeling it came more from the area of the air filter box and the sound was amplified and resonated from under the fuel tank and towards the fairing.

This evening I tried to reproduce the sound and made a small tour.

The first 5 km no sound was to be heard and then it started again. And while going home again the following happened:

- Stationary revs went up to 1500 rpm (1000 rpm normally) and didn't come down or only very slowly
- And sometimes, I had the feeling the engine didn't run on all 3 cylinders
- I also have the feeling after having braked on the engine the above behavior becomes worse

Then at home stationary revs were almost normal again.

I'm a tourer, not a racer and 6'000 rpm is the limit when engine is warm. The bike has 35'000 km

What could be your first thoughts?

Thank you!
Jeroen
 
Last edited:
Sounds like an air leak. Years ago I went to my first club meet and someone said I had an exhaust leak as they could hear a sound. So I pulled it all off and renewed the copper gadgets and used high temp red silicon on all joints. It was still there. The bike was serviced well before all this. I then was off on it to the bush using it as my transport while doing a job. There was someone I knew about 250ks away and so I was heading there and about 5ks from her place the bike suddenly cut to 2 cylinders. After I arrived I pulled the tank for a look around and discovered one missing bolt in the inlet manifold and the other 2 loose and ready to fall out as well. Seems that bloke was right, it had an air leak from GUESS WHO in Sydney who did the service and didn't tighten those Vacuum balance plugs in the inlets. He really was a DICKHEAD. Check your manifold plugs or see if that's now a hose connecting them and it's split.
 
Thank you all for the valuable information!

I have to admit that the weather is more then fine at 30 °C, hence I took the 3C out for a spin today. The weather will stay like this so let's see if I want to go out the coming days or allocate time to investigate the 1000 SFC problem...

I'll keep you updated.

Cheers,
Jeroen
 
My mates 70's BSA Rocket 3 did that while we were on holiday once, sounded like a budgie was trapped in the engine, ran rough too but it turned out that it was just an intake air leak.
 
take tank and seat off, arrange a test fuel tank start engine, spray brake cleaner around the inlet manifold areas and wait to to see where it gets sucked in causing an increase in the revs.
CLEM
 
Finally had some time to look into this.

Removed sparkplugs

Left cyl: blackish
Middle cyl: blackish with white extreme tip of the center (insert) electrode and white extreme tip of the side (ground) electrode
Right cyl: Greyish

Will do the braketest tomorrow
 
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