Bike pinking

[Sylvester]

Hi Folks, just recently retired and moved to France. My bike seems to hate French fuel. It’s a R 80 GS paralever. Engine has a Seibenrock 1000cc conversion with the heads/pistons machined to match by Steve Scrimminger. Still has the std carbs and was running ok in Germany but now pinks like crazy at higher rpm and under load. I can ride around the pinking, but that’s not a long term solution. I already retarded the timing a little in Germany. Plug colour looks ok and in know it’s not running too lean. Starts and runs ok apart from the pinking. Was gonna raise the needles a notch and try retarding a little more. I had the compression checked in Germany and the graph read 10.5:1 but I have no idea how accurate it was. It was done to see if both sides were the same. Any other ideas?

 

[Gelandestrasse]

It could be a bad batch of fuel (from your local filling station) - I've had them abroad. And you could read this: https://bmwmotorcycletech.info/pinging-detonation.htm

 

[Rugged Path]

Bike pinking!

Hopefully not a transgender thing .


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[Greg Masters]

You can't check the compression ratio by doing a compression test!

Try using a tank of branded (eg TotalEnergies) premium fuel and see if the problem continues.

Retarding the ignition isn't the best solution although could be a short term fix.

 

[Sylvester]

It could be a bad batch of fuel (from your local filling station) - I've had them abroad. And you could read this: https://bmwmotorcycletech.info/pinging-detonation.htm

Tried several service stations, so not sure. I did read an article in Germany that stated octane levels of fuel here are a little lower than advertised.

 

[Sylvester]

You can't check the compression ratio by doing a compression test!

Try using a tank of branded (eg TotalEnergies) premium fuel and see if the problem continues.

Retarding the ignition isn't the best solution although could be a short term fix.

The compression test was a long story, I had an issue when I thought one cylinder was running hotter than the other as the headers were widely different colors. I got a bit obsessed with it all tbh. One thing lead to another and a local genius did both the volume and the pressure check to verify all was well. After stripping carbs renewing every thing and setting up, all was well. I always use premium fuels as I’ve had bad experiences in the UK with supermarket stuff and lower octane gas.

 

[cookie]

You could try an octane booster additive.

 

[mikeyboy]

Maybe the bean can advance retard is worn or has weak springs?
Weak springs could make it advance too early in the rev range,worn mech could make it over advance.

 

[Micky]

Maybe the bean can advance retard is worn or has weak springs?
Weak springs could make it advance too early in the rev range,worn mech could make it over advance.

On my 1979 R100RS severe pinking was eventually cured by replacing the points with a Boyer Bransden electronic setup

 

[Sylvester]

Maybe the bean can advance retard is worn or has weak springs?
Weak springs could make it advance too early in the rev range,worn mech could make it over advance.

Could be but when I checked the timing, it does not go beyond the advance markings when i rev the motor.

 

[Sylvester]

You could try an octane booster additive.

Might try it to see if it works.

 

[SteveHop]

Perhaps the compression is a bit high for the French low octaine fuel .
When i asked Siebenrock about taking my bike to Africa , where the petrol is crap ,they advised me to reduce the compression by using a base gasket.
10.5 : 1 sounds very high Siebenrock advertse there gear at 9.5:1 , perhaps you need the 1000 cc heads ?
Have you tried a Octaine booster adative to you fuel to see what happens ?

 

[Mistacat]

You say that the mixture is correct, What did you use to measure the Air Fuel Ratio?
Have you reset the Air Fuel ratio since moving to France.
I assume that you know that the stoichiometric AFR for petrol is 14.7 to 1 and that for E10 it is 14.1 to 1 .
I have found my airhead to be happy at an AFR of 13.8 to 1, High compression 1000cc on 800 heads using E10.

 

[Garry H]

I have altered the advance cure in the beancan on a few airheads in the past to stop this

 

[Nin]

Probably not helpful, but we’re running two airheads with Siebenrock 1000cc kits on Wedgetail ign and French fuel (premium) up in the alps with no problems whatever.


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[Sylvester]

Perhaps the compression is a bit high for the French low octaine fuel .
When i asked Siebenrock about taking my bike to Africa , where the petrol is crap ,they advised me to reduce the compression by using a base gasket.
10.5 : 1 sounds very high Siebenrock advertse there gear at 9.5:1 , perhaps you need the 1000 cc heads ?
Have you tried a Octaine booster adative to you fuel to see what happens ?

Yep, I thought it was very high. I had the heads and pistons machined to match the barrels. It had the 1000 cc kit on it when I bought it. I have no idea how much was taken from the heads or if that was the planed compression. As I was living in Germany at the time, I came over to see my folks and left the heads and barrels at the machine shop and picked them up a few months later.

 

[Sylvester]

Probably not helpful, but we’re running two airheads with Siebenrock 1000cc kits on Wedgetail ign and French fuel (premium) up in the alps with no problems whatever.


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Yeah, tbh I should have just left it as it was.

 

[Sylvester]

You say that the mixture is correct, What did you use to measure the Air Fuel Ratio?
Have you reset the Air Fuel ratio since moving to France.
I assume that you know that the stoichiometric AFR for petrol is 14.7 to 1 and that for E10 it is 14.1 to 1 .
I have found my airhead to be happy at an AFR of 13.8 to 1, High compression 1000cc on 800 heads using E10.

I’m only basing the mixture on the plug color and the feel of the bike. It runs and starts well. I had a lot of carb issues when I first got the bike 17 years ago.

 

[SteveHop]

Yep, I thought it was very high. I had the heads and pistons machined to match the barrels. It had the 1000 cc kit on it when I bought it. I have no idea how much was taken from the heads or if that was the planed compression. As I was living in Germany at the time, I came over to see my folks and left the heads and barrels at the machine shop and picked them up a few months later.

Think when the R80 heads are machined to alter the squish band its like a steep taper coming out to the size of the R100 barrel bore diameter so the effective volume of the cylinder head is less then that of a R100 head so you end up with a higher compression ratio ?

 

[Sylvester]

Think when the R80 heads are machined to alter the squish band its like a steep taper coming out to the size of the R100 barrel bore diameter so the effective volume of the cylinder head is less then that of a R100 head so you end up with a higher compression ratio ?

I have no idea!