Vacuum Release Plate O ring on FCR's.

DaleEO said:

I made a change this afternoon to see if I could get the bike to start easier. It seems lately that it has been a bit rich when starting cold with the choke.

I went to an "S" needle from an "R", and dropped the pilot one step from a 40 to a 38. Bike started great with the choke at around 90 degree's ambient, 30 seconds later it was starting to not quite 8 stroke, but was obviously getting rich, and off came the choke. Once warm I set the pilot screw to 2 & 1/4 turns out, here at the house, and idling smoothly. It also started immediately on the button when warm.

This actually solves a bit of a riddle that I had after coming back down to the desert 3300-4400' from my high mountain riding area of 8500-10,000' this last year. I had increased the pilot size by one, and the main jet by one or two to compensate for the altitude change. The bike ran great, but, would not start on the button when warm with the electric start, I had to use the choke to get to start warm with the electric start, but, would start straight away with the kicker without the choke.

Simple right? Just increase the size of the pilot again as it was obviously too lean. However, when I did this the next larger size was too rich, (pilot screw too far in), and the other was a bit too lean, ( pilot screw too far out). So I went from the "S" needle I was running up in the mountains to the "R" needle and the hot starting problem was solved. Or so I thought.

Hind sight being what it is, now that I have changed the O ring on the vacuum release plate I can clearly see that I had bit of an air leak. So by covering this air leak with the richer R needle, it made the bike a tad too rich to start with the choke when kicking it.

There was an article in the American publication Dirt Rider or Dirt Bike some time back, and Ty Davis was showing you how to refurbish your FCR carb. He warned against getting any contact, or especially Brake cleaner on this vacuum release plate O ring as it would damage it.

They're not cheap, at $30 bucks, but, it's something worth checking into if you have some hours on your bike.

Dale

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sparks said:

DaleEO said:

I made a change this afternoon to see if I could get the bike to start easier. It seems lately that it has been a bit rich when starting cold with the choke.

I went to an "S" needle from an "R", and dropped the pilot one step from a 40 to a 38. Bike started great with the choke at around 90 degree's ambient, 30 seconds later it was starting to not quite 8 stroke, but was obviously getting rich, and off came the choke. Once warm I set the pilot screw to 2 & 1/4 turns out, here at the house, and idling smoothly. It also started immediately on the button when warm.

This actually solves a bit of a riddle that I had after coming back down to the desert 3300-4400' from my high mountain riding area of 8500-10,000' this last year. I had increased the pilot size by one, and the main jet by one or two to compensate for the altitude change. The bike ran great, but, would not start on the button when warm with the electric start, I had to use the choke to get to start warm with the electric start, but, would start straight away with the kicker without the choke.

Simple right? Just increase the size of the pilot again as it was obviously too lean. However, when I did this the next larger size was too rich, (pilot screw too far in), and the other was a bit too lean, ( pilot screw too far out). So I went from the "S" needle I was running up in the mountains to the "R" needle and the hot starting problem was solved. Or so I thought.

Hind sight being what it is, now that I have changed the O ring on the vacuum release plate I can clearly see that I had bit of an air leak. So by covering this air leak with the richer R needle, it made the bike a tad too rich to start with the choke when kicking it.

There was an article in the American publication Dirt Rider or Dirt Bike some time back, and Ty Davis was showing you how to refurbish your FCR carb. He warned against getting any contact, or especially Brake cleaner on this vacuum release plate O ring as it would damage it.

They're not cheap, at $30 bucks, but, it's something worth checking into if you have some hours on your bike.

Dale

Click to expand...

Hi Dale,

There you go, I told you that it would make a big difference, now all your carb settings are the same as mine, apart from the 2 1/4 turns on the FS, I'm on 1 1/2, if you were so far in with the FS before you got a reaction from the engine this says it's to rich on the PJ, was this test when you were on the 40PJ?.
Now you have fitted the new O ring you should find the FS more sensitive to small changes.
But we still have the big question how much does US gas differ from European gas, when burnt that is.
I presume your stator has turned up for you to run the engine up?.

Regards

Sparks.

Click to expand...

Taffy said:

its ok steve, dale followed a hunch and hes found out. solid stuff!

now he's on 38s as well i'm happy that the three lads that do the most testing here (except perhaps buzzard to be fair) are all really mean and lean!

i think he has an unfair advantage as well. he can learn a sh... load by going up and down a mountain! i have a only a 100ft difference in the whole of cambridgeshire!

print em a photo of the fens for us steve!!! preferably a 'fen blow' just like that old james stewart film about oklahoma film from the 30s!

nice one dale. BTW you may want to chnage the chock jet. go look at my description of the choke in the doc for this...

as fuel. yes there is a difference but the bikes fuel i would say is more dictated by altitude and humidity than the fuel. it's like we're worried about the size of the load in fred's barrow when we should be worried about the weight of what's in fred's barrow!

regards

Taffy

Click to expand...

DaleEO said:

sparks said:

DaleEO said:

I made a change this afternoon to see if I could get the bike to start easier. It seems lately that it has been a bit rich when starting cold with the choke.

I went to an "S" needle from an "R", and dropped the pilot one step from a 40 to a 38. Bike started great with the choke at around 90 degree's ambient, 30 seconds later it was starting to not quite 8 stroke, but was obviously getting rich, and off came the choke. Once warm I set the pilot screw to 2 & 1/4 turns out, here at the house, and idling smoothly. It also started immediately on the button when warm.

This actually solves a bit of a riddle that I had after coming back down to the desert 3300-4400' from my high mountain riding area of 8500-10,000' this last year. I had increased the pilot size by one, and the main jet by one or two to compensate for the altitude change. The bike ran great, but, would not start on the button when warm with the electric start, I had to use the choke to get to start warm with the electric start, but, would start straight away with the kicker without the choke.

Simple right? Just increase the size of the pilot again as it was obviously too lean. However, when I did this the next larger size was too rich, (pilot screw too far in), and the other was a bit too lean, ( pilot screw too far out). So I went from the "S" needle I was running up in the mountains to the "R" needle and the hot starting problem was solved. Or so I thought.

Hind sight being what it is, now that I have changed the O ring on the vacuum release plate I can clearly see that I had bit of an air leak. So by covering this air leak with the richer R needle, it made the bike a tad too rich to start with the choke when kicking it.

There was an article in the American publication Dirt Rider or Dirt Bike some time back, and Ty Davis was showing you how to refurbish your FCR carb. He warned against getting any contact, or especially Brake cleaner on this vacuum release plate O ring as it would damage it.

They're not cheap, at $30 bucks, but, it's something worth checking into if you have some hours on your bike.

Dale

Click to expand...

Hi Dale,

There you go, I told you that it would make a big difference, now all your carb settings are the same as mine, apart from the 2 1/4 turns on the FS, I'm on 1 1/2, if you were so far in with the FS before you got a reaction from the engine this says it's to rich on the PJ, was this test when you were on the 40PJ?.
Now you have fitted the new O ring you should find the FS more sensitive to small changes.
But we still have the big question how much does US gas differ from European gas, when burnt that is.
I presume your stator has turned up for you to run the engine up?.

Regards

Sparks.

Click to expand...

HI Steve,

I think the main reason for our difference on the pilot screw is the fact that you have the adjustable pilot air jet, and have it cut down from the stock 100 which I am running. So, since you have less air you need less fuel. I also want to try the adjustable paj, but, the last time I had the carb off for cleaning, the paj was stuck, and I kind of knackered the slot for the screwdriver, so I quit before I totally ruined it. I will save that adventure for another day. On the stand, I can tell there is a bit of a lean spot right off idle as Taffy has mentioned before, but, I don't notice it when I'm riding. But, never the less, I will make the change to the paj eventually.

The stator has not turned up yet, however, I couldn't wait to try out the motor with the replaced O ring, and my new/used parts, 06 tank, 07 radiator, and the new fan kit. While slightly off topic here, I got the motor hot enough to actuate the fan, and was watching the voltage at the battery before the fan came on and after it was on. Before I started the bike, the voltage was 12.75. After I started the bike the voltage was 13.75 before the fan came on. Once the fan came on the voltage dropped to 12.96 at idle, but, came back up to 13.3 with motor revved up a bit, say 2000rpm's. Once I get your rewound stator I will run the same test for comparison and post the results.

How's the leg coming along??

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