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Old 04-26-2005, 07:23 PM   #1666
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Originally posted by daniz24
Thanks. Btw, BRB sets did a good job on last Sunday Super Touring Race by winning the A Main and B Main.
Congratulation.


Keep them coming..
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Old 04-28-2005, 11:05 PM   #1667
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TG/Guys,

I'm having problems with my Palmaris P/S kits.

Both of my JP FX T-03 are fitted with the Palmaris kits, but no matter how I tune them, I get amazing bottom end power (actually too much) and good top end, but only if I lean the top a lot.

Yesterday I tried to tune both motors at the track. The air temp was 18C, I used a 6TF plug, 16% fuel and 0.3mm head clearence (measured with solder wire).
I started out by tuning the LSN so that the motor wouldn't richen up after being left to idle for 20 seconds, i.e. after 20 seconds of idiling I hit the throttle and the engine reved up without spluttering.

Then I went on to tune the HSN, I was running approx 5.5 turns at first, but the engine was just four stroking.
I leaned out the HSN more and it started to run nicely at about 75C - too cold, though. I leaned it out further, but at 85C it started going lean.

Suspecting that my LSN was just too rich, I leaned it down as much as I could - I got it down to 1.5 turns, but then the motor wouldn't even run at idle, so I ended up at 2 turns out.
This made virtually no difference, though - the bottom end was balistic, it was actually at the point where it was virtually uncontrollable and I had to put loads of pre-tension on my clutch spring and even so it simply lept out of the corners.
But as soon as the motor hit 85-90C, it just went lean.

I tried the motor at a head clearence of 0.4mm, too and this made little or no difference.

I can't believe that I have carb problems on both motors, especially as one motor had only even been run at the winternats. Both motors behave in exactly the same way.

I've made the LSN rich and lean and on my track it made no difference or little difference to the temperature at which the motor started to lean out on the track.

To me, it would almost sound like I need more head shims??

Thanks for the help, Mark.
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Old 04-29-2005, 02:28 AM   #1668
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Quote:
Originally posted by markp27
TG/Guys,

I'm having problems with my Palmaris P/S kits.

Both of my JP FX T-03 are fitted with the Palmaris kits, but no matter how I tune them, I get amazing bottom end power (actually too much) and good top end, but only if I lean the top a lot.

Yesterday I tried to tune both motors at the track. The air temp was 18C, I used a 6TF plug, 16% fuel and 0.3mm head clearence (measured with solder wire).
I started out by tuning the LSN so that the motor wouldn't richen up after being left to idle for 20 seconds, i.e. after 20 seconds of idiling I hit the throttle and the engine reved up without spluttering.

Then I went on to tune the HSN, I was running approx 5.5 turns at first, but the engine was just four stroking.
I leaned out the HSN more and it started to run nicely at about 75C - too cold, though. I leaned it out further, but at 85C it started going lean.

Suspecting that my LSN was just too rich, I leaned it down as much as I could - I got it down to 1.5 turns, but then the motor wouldn't even run at idle, so I ended up at 2 turns out.
This made virtually no difference, though - the bottom end was balistic, it was actually at the point where it was virtually uncontrollable and I had to put loads of pre-tension on my clutch spring and even so it simply lept out of the corners.
But as soon as the motor hit 85-90C, it just went lean.

I tried the motor at a head clearence of 0.4mm, too and this made little or no difference.

I can't believe that I have carb problems on both motors, especially as one motor had only even been run at the winternats. Both motors behave in exactly the same way.

I've made the LSN rich and lean and on my track it made no difference or little difference to the temperature at which the motor started to lean out on the track.

To me, it would almost sound like I need more head shims??

Thanks for the help, Mark.
Your bottom end sounds good. Thats how it should be out of corners etc. Did you check the barrel for twist like I mentioned on 3hobby? This is a common problem with the layout of the serpent cars. Even bending the throttle connection rod if the carb is angled it will get slightly twisted as it slides out. With enough temp this slight twist will allow air leak in through the barrel runners. Try to get the carb as straight as possible even if you have to remove the rollover handle. As you know myself and Chris ran Serpents for the last few years and we had to change several carbs because they had become so loose at the barrel. All 3 carbs ran fine with standard engines at lower temps but as soon as we put in BRB the problem came out with the higher temps.

Also, what pipe/header set are you using?
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Old 04-29-2005, 02:38 AM   #1669
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If air was getting in though, it would mean that I would have the HSN/LSN needle setting richer than normal, to counteract the extra air that would be getting in.

But my HSN setting looks very lean. Opening up the HSN so it is flush with the HSN holder, the engine runs incredibly rich. Even when it is turned in quite a way, the engine still doesn't pick up at the top end (bottom end remains fine, though).
Then when the engine starts to run well (at about 75-80C), I can only lean out the HSN a little more before it acts very lean.

Do you mean if the carb is facing straight ahead? If so, then yes, I always mount the carb to face directly forwards.

I'm using the EFRA 2601 pipe from JP.

Cheers, Mark.
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Old 04-29-2005, 05:47 AM   #1670
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Quote:
Originally posted by markp27
If air was getting in though, it would mean that I would have the HSN/LSN needle setting richer than normal, to counteract the extra air that would be getting in.

But my HSN setting looks very lean. Opening up the HSN so it is flush with the HSN holder, the engine runs incredibly rich. Even when it is turned in quite a way, the engine still doesn't pick up at the top end (bottom end remains fine, though).
Then when the engine starts to run well (at about 75-80C), I can only lean out the HSN a little more before it acts very lean.

Do you mean if the carb is facing straight ahead? If so, then yes, I always mount the carb to face directly forwards.

I'm using the EFRA 2601 pipe from JP.

Cheers, Mark.
hopefully, all will be sorted now. Smaller head should make the difference.
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Old 04-29-2005, 05:54 AM   #1671
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My old JP FX donor engine is going to look even more strange with a Novamega head on it
Yep, hopefully this means I can then run the HSN a bit richer and also get the temperature up.

Cheers, Mark.
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Old 04-29-2005, 06:22 AM   #1672
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Mark, what's your ambient track temp at the current moment?

You mentioned that your low end is good. But when you start leaning the HSN, the engine goes lean. That would suggest that when you start to lean your HSN, you actually indirectly leaning your LSN too.

When you find your LSN goes lean when you tune the HSN, try richen the LSN by 5 minute or so. Richen it till the engine idles nicely. Try lowering the idle a little at the same time to see if it helps calm the engine down.

If it's still giving you problems like this, try a colder 7tf plug.

There are times when you cannot tune by temp. And perhaps this is one of those times. Try tuning the engine by the sound of it. See if the engine sounds and revs happily at that particular carb setting and does not complain. I would stick to this setting whatever the temp tells me.
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Old 04-29-2005, 07:18 AM   #1673
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Quote:
Originally posted by InitialD
Mark, what's your ambient track temp at the current moment?

You mentioned that your low end is good. But when you start leaning the HSN, the engine goes lean. That would suggest that when you start to lean your HSN, you actually indirectly leaning your LSN too.

When you find your LSN goes lean when you tune the HSN, try richen the LSN by 5 minute or so. Richen it till the engine idles nicely. Try lowering the idle a little at the same time to see if it helps calm the engine down.

If it's still giving you problems like this, try a colder 7tf plug.

There are times when you cannot tune by temp. And perhaps this is one of those times. Try tuning the engine by the sound of it. See if the engine sounds and revs happily at that particular carb setting and does not complain. I would stick to this setting whatever the temp tells me.
Tried this already. Richening the LSN wasnt having any effect. The JP head is too big. Up to 20deg C ambient we are running with JP heads minus 3 or 4 fins.
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Old 04-29-2005, 08:04 AM   #1674
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Hi D,

Like PRE says, I also tried richening the LSN and found it had no or little effect on my HSN or temp. I think this is because the track is large and fast, i.e. mostly full throttle.

I'm going to try sticking on the Novamega head and if necessary wrapping the head in tin foil to see what the effect is.

Would a 7TF not exagerate the effect I'm seeing - I thought it would increase the bottom end even more? Or am I thinking in the wrong direction?

Cheers, Mark.
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Old 04-29-2005, 09:12 AM   #1675
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Quote:
Originally posted by markp27
TG/Guys,

I'm having problems with my Palmaris P/S kits.

Both of my JP FX T-03 are fitted with the Palmaris kits, but no matter how I tune them, I get amazing bottom end power (actually too much) and good top end, but only if I lean the top a lot.

Yesterday I tried to tune both motors at the track. The air temp was 18C, I used a 6TF plug, 16% fuel and 0.3mm head clearence (measured with solder wire).
I started out by tuning the LSN so that the motor wouldn't richen up after being left to idle for 20 seconds, i.e. after 20 seconds of idiling I hit the throttle and the engine reved up without spluttering.

Then I went on to tune the HSN, I was running approx 5.5 turns at first, but the engine was just four stroking.
I leaned out the HSN more and it started to run nicely at about 75C - too cold, though. I leaned it out further, but at 85C it started going lean.

Suspecting that my LSN was just too rich, I leaned it down as much as I could - I got it down to 1.5 turns, but then the motor wouldn't even run at idle, so I ended up at 2 turns out.
This made virtually no difference, though - the bottom end was balistic, it was actually at the point where it was virtually uncontrollable and I had to put loads of pre-tension on my clutch spring and even so it simply lept out of the corners.
But as soon as the motor hit 85-90C, it just went lean.

I tried the motor at a head clearence of 0.4mm, too and this made little or no difference.

I can't believe that I have carb problems on both motors, especially as one motor had only even been run at the winternats. Both motors behave in exactly the same way.

I've made the LSN rich and lean and on my track it made no difference or little difference to the temperature at which the motor started to lean out on the track.

To me, it would almost sound like I need more head shims??

Thanks for the help, Mark.
Mark, what is the timing on induction? Opening and closing.
Sound to me that it is not closing on time. Try to mesure it +/- 1 degree is OK.
Edward
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Old 04-29-2005, 09:15 AM   #1676
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TopGun, I'm a bit of a beginner on this timing stuff - how do I measure this?

Also, the combustion chamber is very black, what would cause this:

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Old 04-29-2005, 09:18 AM   #1677
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You can probably see, too, from the picture that the HSN is turned in pretty far.

Cheers, Mark.
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Old 04-29-2005, 09:33 AM   #1678
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Quote:
Originally posted by Top Gun 777
Mark, what is the timing on induction? Opening and closing.
Sound to me that it is not closing on time. Try to mesure it +/- 1 degree is OK.
Edward
Ed, I believe Mark is running the original JP FX black coated crankshaft. I believe a lot have run this crankshaft with the BRB successfully over here. But not at lower 16% nitro... I don't know how true it is but there have been some reports saying that the JP does not work good with lower nitro content.
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Old 04-29-2005, 09:37 AM   #1679
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I've not had any problems with the original JP sleeve/crankshaft, D - it was a real rocket. It was very easy to tune with the 16%. The only time I had problems was in Florida during the winternats and that was with 30% fuel.
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Old 04-29-2005, 09:38 AM   #1680
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Quote:
Originally posted by markp27
TopGun, I'm a bit of a beginner on this timing stuff - how do I measure this?
Ummmm... You need to mount the crankshaft to a protractor for that.

Quote:
Originally posted by markp27
Also, the combustion chamber is very black, what would cause this:
Mine is also like that in the pic after a hard run. Is the plug condition ok? Coil pressed in or out?

p/s: Geez... Did your dirt filter expired?
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