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Old 04-08-2004, 07:52 AM   #7951
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Default Re: Titanium screws

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Originally posted by KevinS
HPI... Hopeless Parkinglot Invaders
Oh... my... gawd...
That is hilarious !!!

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Old 04-08-2004, 07:58 AM   #7952
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Quote:
Originally posted by Palmaris Europe
Lapping is were you reduce the overall diameter of the piston to remove some of the pinch at the top of the sleeve. People believe a tighter pinch is better but this is far from correct. All you really want is enough pinch to create the combustion process. Excess pinch actually puts strain on the engine on initial start ups which is why most engines dont last any length of time and also why people reccommend changing the conrod after break in.

If the piston is lapped correctly the engine will last a lot longer and you shouldnt need to change the conrod after break in.
Hiya, Palmaris !

Uhhmmm... still don't know what you mean by "lapping in the piston"... can you explain the process please? As well as benefits and drawbacks.

About "changing the conrod after break-in"... I know you probably didn't mean it this way, but this makes it sound like you must change your conrod after break-in if you don't use a lap-in method. I have run in my engines in many different ways (best way is WOT method to heat-cycle) and have never had to change a conrod after break-in.
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Old 04-08-2004, 08:19 AM   #7953
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Quote:
Originally posted by GlennCauley
Hiya, Palmaris !

Uhhmmm... still don't know what you mean by "lapping in the piston"... can you explain the process please? As well as benefits and drawbacks.

About "changing the conrod after break-in"... I know you probably didn't mean it this way, but this makes it sound like you must change your conrod after break-in if you don't use a lap-in method. I have run in my engines in many different ways (best way is WOT method to heat-cycle) and have never had to change a conrod after break-in.
Lapping the piston is were you reduce the overall diameter of the outside of the piston. Its like sticking a bar in a lathe and turning it down to a smaller size. The big difference being lapping the piston is a more delicate process and requires extreme caution. Reducing the size of the piston also reduces the length of time the piston needs to bed itself to the sleeve hence faster run-in times.

The benefits are that the engine will not have the same stress inflicted on it so wear is reduced and longetivity of the engine increases. Due to not having the same friction between the P/S the engine will not have to work as hard during runs which in theory should also help increase RPM's.

The drawback of lapping is getting it wrong . Take off too much material and you end up loosing all compression. Result is as you know an engine that doesnt run.

You are absolutely correct. I didnt mean it as it must appear. There is no need to change a conrod after break-in ever but this is recommended by the manufacturer because the stress from break-in weakens the rod or creates excessive wear on the bushing.
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Old 04-08-2004, 08:38 AM   #7954
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Quote:
Originally posted by Palmaris Europe
Lapping the piston is were you reduce the overall diameter of the outside of the piston. Its like sticking a bar in a lathe and turning it down to a smaller size.
So to do this you have to turn the piston in a lathe?


Not something that people can do at home, is it?

I understand the theory, but I am still confused exactly how you DO this.
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Old 04-08-2004, 08:46 AM   #7955
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Quote:
Originally posted by GlennCauley
So to do this you have to turn the piston in a lathe?


Not something that people can do at home, is it?

I understand the theory, but I am still confused exactly how you DO this.
There is a little hand held tool you can buy to make it easier. Dont need a lathe. I have only ever saw them on ebay or made by TopGun.

Never seen them on sale in shops before. This is the main reason why most people never have heard about it or even try doing it.
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Old 04-08-2004, 09:11 AM   #7956
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Quote:
Originally posted by GlennCauley
I think there is confusion here.
The question was about the length of the pressure line (pipe to tank), not the fuel line (tank to carb).

A longer fuel line (tank to carb) will help a flipped-over car run longer, since there will be more fuel in the line. However, there may be limitations to the length of fuel line you can use (especially at big races) because you are in essence increasing the fueltank capacity above the 75cc limit.

A longer pressure line will help to "soften" the pressure pulses going from the pipe into the tank. This will help to maintain a more even pressure of the fuel system, which makes for smoother operation (especially at idle). Note that this will result in a less-pressurized fuel system, since you are increasing the volume of the "pressure chamber" which results in decreased pressure. It is a trade-off. I have always used a pressure line at least 8~10" long.

Try this... put a really short pressure line between pipe and tank. Run the car, then come in and with the car off the ground blip the throttle... watch the effect on the fuel in the tank. It may "ripple" the fuel because of the high pressure.
Then install a long pressure line and repeat the process. The effect on the fuel will be dramatically less... no "ripples" in the fuel.
Thanks for the tip
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Old 04-08-2004, 12:53 PM   #7957
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Default rear diff

No matter how I assemble it, clean it, pre load it, I can't get the smooth and loose feeling it had before. WHAT CAN IT BE!!
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Old 04-08-2004, 01:27 PM   #7958
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Quote:
Originally posted by Palmaris Europe
There is a little hand held tool you can buy to make it easier. Dont need a lathe. I have only ever saw them on ebay or made by TopGun.

Never seen them on sale in shops before. This is the main reason why most people never have heard about it or even try doing it.
How about Brasso or a fine lapping compound, surely this would be better, just make sure everything is properly flushed before reassembly. You really need to maintain the cross hatch pattern within the sleeve as well to maintain correct lubrication of piston and sleeve.
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Old 04-08-2004, 02:05 PM   #7959
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Quote:
Originally posted by Diesel Racer
How about Brasso or a fine lapping compound, surely this would be better, just make sure everything is properly flushed before reassembly. You really need to maintain the cross hatch pattern within the sleeve as well to maintain correct lubrication of piston and sleeve.
A lapping compound is required anyway. But the tool makes it a much easier process.
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Old 04-08-2004, 06:41 PM   #7960
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I believe the tool that Palmaris is talking about is basically a stick with a suction cup on the end. We use these sometimes in our shop to quickly lap in valves for a quick fix.
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Old 04-08-2004, 06:56 PM   #7961
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Quote:
Originally posted by SupermaxxRich
I believe the tool that Palmaris is talking about is basically a stick with a suction cup on the end. We use these sometimes in our shop to quickly lap in valves for a quick fix.
Still, I'm assuming that this process requires some sort of a turning machine or a lathe ...

Maybe Glen is right, not something everyone can do at home.
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Old 04-08-2004, 08:25 PM   #7962
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Quote:
Originally posted by GlennCauley
I think there is confusion here.
The question was about the length of the pressure line (pipe to tank), not the fuel line (tank to carb).

A longer fuel line (tank to carb) will help a flipped-over car run longer, since there will be more fuel in the line. However, there may be limitations to the length of fuel line you can use (especially at big races) because you are in essence increasing the fueltank capacity above the 75cc limit.

A longer pressure line will help to "soften" the pressure pulses going from the pipe into the tank. This will help to maintain a more even pressure of the fuel system, which makes for smoother operation (especially at idle). Note that this will result in a less-pressurized fuel system, since you are increasing the volume of the "pressure chamber" which results in decreased pressure. It is a trade-off. I have always used a pressure line at least 8~10" long.

Try this... put a really short pressure line between pipe and tank. Run the car, then come in and with the car off the ground blip the throttle... watch the effect on the fuel in the tank. It may "ripple" the fuel because of the high pressure.
Then install a long pressure line and repeat the process. The effect on the fuel will be dramatically less... no "ripples" in the fuel.
Im no engine master, so if there is a master(Im sure its you TG) pls correct me if Im wrong.

Pressure Line (pipe to tanks) is some kind connecting link to make a close circuit between tank, engine and pipe.
Its called a equalizer also, equalizing the pressure between pipe and tanks.

When Idle, it only acts as a breather hole so carb can sucks the fuel.

In mid rpm/throttle opening (this is what Sow&Steady call as a black art) depends on the divergent cone (pipe) design it acts like a booster, its carry the pressure from the pipe (pump) and blows the tanks. In this stage, this condition explains why tuning the mid rpm is sometimes difficult.
So in my opinion, the longer is better(10" is max). Longer=smoother coz it can reduce the pulsation effect from the pipe. Longer=bigger volume, when the pipe pressure is to much for carb, it acts like a "residual pressure tank". And will gave the pressure instantly when more throttle is opened. This is very similar princip when Yamaha releasing the Yamaha Energy Induction System (YEIS) and using same theory like Capacitor in power electronic circuit.

After 3/4 till WOT, it acts as a limiter/regulator, controls how much fuel allowed to enter the carb. (Try to make a WOT on .21 engine then immediately pull-off the line, see what happen) Remember that our engine is using diesel 2 stroke principal, so the (Delta t) is still can make the engine to overrevving.
So in my opinion, the longer is still better. The 21 guy is even put a filter to make the effect even smoother.

Like uncle Sow mentioned the effect is very subtle, I guess we better adjust another thing to make our engine work better.
All above is base on my theory and experience. And there is another factor that can change the performance. Tuned pipe is playing biggest part in this section.

Just my 2 cents.
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Old 04-08-2004, 08:35 PM   #7963
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Quote:
Originally posted by Sow&Steady
Maybe Glen is right, not something everyone can do at home.
It is a black art !
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Old 04-08-2004, 08:46 PM   #7964
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Default Re: rear diff

Quote:
Originally posted by cox049
No matter how I assemble it, clean it, pre load it, I can't get the smooth and loose feeling it had before. WHAT CAN IT BE!!
This is what I think happens...

Did you use any lube on the diff balls the first time you install the diff? I recommend using the Mugen Super Grease. I use it on my Centax thrust bearings and they are excellent. I only rub a thin layer on the diff balls before assembly.

But the trick is you need to do it the FIRST TIME. If you didn't, no matter how much lube or how many times you service it, the diff will remain gritty. I guess when you did not lube it the first time, the diff balls and the plates would already have "flat spots" which will still remain even after you lube it. That's the one that makes the diff gritty. I guess it's ok to have a gritty diff (need somebody else to confirm this) but if you want to make them like new again, replace the balls. Lube it with sparingly with the Mugen Super Grease and be done with it. I believe Serpent is coming out with 4 mm ceramic coated diff balls (1378) for the diff.

I still have mine very smooth as from day one and I have not needed to open it up to service it yet.
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Old 04-08-2004, 08:49 PM   #7965
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Default Re: Titanium screws

Quote:
Originally posted by KevinS
I know some of you use titanium screws on your cars and I have been looking for a place that sells them. So far my search has only come up with complete sets (but none for Serpent). Unfortunately my source for aluminum screws (www.fastener-express.com) doesn't have any titanium.

I know HPI has packages of 5 (for $6!) but I am hesitant since I own Serpents, not Hopeless Parkinglot Invaders. That and I can't stop but think there must be a place where these screws are cheaper... Since I've seen full sets of 130 screws for ~$60

I'm looking for selftapping screws (prefer hex over philips) and an assortment of M3 screws. Is there anyone who can guide me to a good online shop for this? Thanks
Have you tried Integy?
They sell their titanium screws 10 for $7.99
http://integy.automated-shops.com/cg...57104470616.80

My bad.
I didn't see that you wanted allen head.
I think the Integy ones are all philips.

Last edited by PSI Racing; 04-08-2004 at 09:08 PM.
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