Jug question

GoldenMotor.com

woogie_man

New Member
Aug 9, 2013
223
0
0
Fargo, ND
Hey guys,

Say I have started my build and am starting to work on the motor as well. I have one of the flying horse motors, unsure of generic name. I have the jug of and an planning on taking the piston and opening the ports. Though when I look at the piston through the intake port the piston just about covers the entire port! Now I ripped apart my motor some time ago and removed the base gasket, between the crank case and jug. My main question is I know I need the gasket, but am wondering what thickness do I need?

Looking at performance and reliability.
 

Davezilla

New Member
Mar 15, 2014
2,705
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0
San Antonio Texas
Actually this is a good point for fine tuning your engine's port timing and you can usually get a few more degrees port duration by lifting the jug (using a shim at a specific thickness or double gaskets). What you can tune for in this area is if you want more low end torque, use a thinner gasket, but if you want a little more on top, use a thicker gasket or use 2 gaskets.
Juice Motorparts sells copper base gaskets in both .025" and .016" and these can be used alone or stacked to fine tune your port duration. I'm using a .025 and a .016" base gasket on mine with a .040" thick aluminum shim to put my ports where I wanted them to be.
You can also deck the bottom of the cylinder on a lathe or a mill if you have access to one or you can have a machine shop mill the bottom to true it up better (I had to cut off nearly .040" to get my cylinder base true so that's why the .040" shim) then stack a few of these copper gaskets to get the hight where you want it to be. It usually takes about .040" (1mm) above stock to see a difference in high rpm power, but you can go higher or lower to suit your needs. Cutting the cylinder base or removing the gasket here is NOT a good place to add more compression since it does effect port timing and duration, but if you need to raise your cylinder up by 1mm or more, you can remove the same amount from the top of the cylinder to keep the geometry the same or to adjust for squish clearance.
When I set mine up with the ports where I wanted them to be my piston was sticking up about 1mm above the deck (I cut .056" off the deck when that jug was on a different engine, but it worked so well I wanted to use it on my second build) so I had to stack a .016" and a .025" head gasket and use a shim on top as well to get the desired squish clearance of .75mm or .030" with the port timings where I wanted them to be with the cylinder raised up .041" above stock.

So, if you want more top end power, raise the jug by .041" by using a .016 and a .025" base gasket, I "glued" the 2 gaskets together with a thin coat of Indian Head Gasket Shellac to ensure a perfect seal, and the copper sealed against the jug and base perfectly too. Raising the jug does the same thing as raising the roof osn the exhaust And transfer ports, but also raises the floor on the intake port so this area would need to be dremeled out the same amount you raise the jug or more to get your intake duration back.

If you want more low rpm power (torque) you can true up the base and lower it down about .040" and keep the piston just below the deck, then adding a .016" copper head gasket up top would give you a really good compression ratio as well as a nice tight squish band. Doing this effectively lowers the roof on the exhaust and transfers and lowers the floor on the intake so the intake will have about 12 degrees more intake duration but the exhaust and transfers will lose about 12 degrees duration so this makes the engine pull harder but it'll lose some top end power and rpm.

Here's the link for the copper gaskets you'd need to do this mod, it does save you a LOT of dremel time when raising the jug since all you need to do really is lower the intake floor or cut out another milimeter from the bottom of the piston skirt to keep the timing there the same as before... http://juicemotoparts.com/products/copper-base-gasket-for-motorized-bicycle-engine.html Just follow the links to see the rest of them. Also, only the base and head gaskets are solid copper, the rest of his gaskets are rubberized paper coated with copper gasket spray... you can do that at home with a can of copper gasket spray on stock gaskets to save a few bucks.

Hope you got all that... I can explain it all but I'd have to write a fairly thick book to do so...
 

woogie_man

New Member
Aug 9, 2013
223
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Fargo, ND
That explains it nicely. Will need or and see what I can't find for material.

So higher jug for higher power, but les torque.
Lower jug for higher torque, but less power.
 

mapbike

Well-Known Member
Mar 14, 2010
5,502
109
63
Central Area of Texas
And the there is the fact that there are multiple jugs for these engine and some have ports timed for better high rpm power and some have ports positioned for better low end power....

Not trying to add any confusion to Daves excellent instructions, but Im finding that each of the 38mm stroke engines and the 40mm stroke engines all have different port timings with the same jug on them, so depending on what engine you have and depending on what jug you have will determine what mods of jug or combination of gasket thicknesses will be ideal.

Im finding that with these 3 different engine geometries and the multiple types of jugs out there we truly dont have a one size fits all when it comes to setting the engine up for how you want it to run.

Each jug and engine geometry will require things to be done a little different to get the desired results and honestly I haven't experimented enough yet to know what is best for each combination, I sure wish I knew for sure but Im starting a whole new learning process with some of this myself....lol

The info Dave shared in his post is great information and for sure gives the basic idea of what needs to be done to get any of these engines to perform better either down low or in higher rpms.
 

woogie_man

New Member
Aug 9, 2013
223
0
0
Fargo, ND
The one I have is the flying horse model. I was able to pick up some gasket material, as well as some of the schelac that was mentioned. I have enough material that u can play with it and see what I come up with.
 

mapbike

Well-Known Member
Mar 14, 2010
5,502
109
63
Central Area of Texas
The one I have is the flying horse model. I was able to pick up some gasket material, as well as some of the schelac that was mentioned. I have enough material that u can play with it and see what I come up with.
II dont know what the jug on a Flying Horse engine looks like as far as port position, I think theFlying Horse engines are GT5/38mm stroke.

Best wishes on the experimenting, hope it works out to be a good running engine for you when you get it done.
 

Davezilla

New Member
Mar 15, 2014
2,705
10
0
San Antonio Texas
And the there is the fact that there are multiple jugs for these engine and some have ports timed for better high rpm power and some have ports positioned for better low end power....

Not trying to add any confusion to Daves excellent instructions, but Im finding that each of the 38mm stroke engines and the 40mm stroke engines all have different port timings with the same jug on them, so depending on what engine you have and depending on what jug you have will determine what mods of jug or combination of gasket thicknesses will be ideal.

Im finding that with these 3 different engine geometries and the multiple types of jugs out there we truly dont have a one size fits all when it comes to setting the engine up for how you want it to run.

Each jug and engine geometry will require things to be done a little different to get the desired results and honestly I haven't experimented enough yet to know what is best for each combination, I sure wish I knew for sure but Im starting a whole new learning process with some of this myself....lol

The info Dave shared in his post is great information and for sure gives the basic idea of what needs to be done to get any of these engines to perform better either down low or in higher rpms.
No problem here... you can add anything that needs to be added or correct anything I may have made a mistake on... It's the arrogance of some or cluelessness of others that tend to annoy me, but any intelligent additions or corrections are always welcome...

Yeah, I've noticed the same things... even if you got 2 40mm stroke bottom ends, the piston may sit in the cylinder higher or lower at TDC due to the base hight being slightly different so one jug may work very well on one bottom end but the piston may stick up past the deck or end up further down in the jug at TDC, which also places the ports at different places respectively... This can save someone a lot of time cutting to raise an exhaust or set of transfers roofs in some cases or it could lower the port roof by swapping jugs on a particular bottom end to get more torque down low. pretty much if you can get a nice bottom end from one supplier and if you got a few jugs from different suppliers you can set your port hights as easily as swapping jugs until you get them where you want them and eliminate the need to raise a port or shim the base or cut down the base or the deck, but one would need to keep their extra jugs labled as far as who they bought from and what the measurements are etc to be able to keep track of which ones have the ports at what location etc...
Of course, most of us just buy the engine then either start cutting or shimming until things fit perfectly or until the ports open at a certain crank position, but for somebody who has a lot of parts from different vendors it would be an easy time saver by fitting and measuring to see which combo would put the ports in the right location for the type of build being done.

Pretty much the only real consistancy I've seen across most vendors is in the pistons, but it seems each vendor gets the cylinders or cases from different sources and these sources all have their own set of dimensions that they go by, which is good for mixing and matching to get the desired geometries, but they're also usually close enough that any jug can be made to work on any bottom end without doing serious modifications.
 

woogie_man

New Member
Aug 9, 2013
223
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0
Fargo, ND
New seals made... but when getting the piston rims on I snapped one. So note have to wait for more rings. Also mounted up the whalboro carb .. need to weld the crank to the frame and run cables.
 

woogie_man

New Member
Aug 9, 2013
223
0
0
Fargo, ND
Lol.

Well found out my bottom bracket is seized up. Have a replacement set, but unable to get old unit apart. On the hunt for a replacement.
 

woogie_man

New Member
Aug 9, 2013
223
0
0
Fargo, ND
Yah I was able to find a bottom bracket cylinder for $10 shipped. It is a raw metal do will be able to wild up and get on there good this time. My gaskets, and find should be here Monday, and the bracket will be here Friday. So that will give me a good week to get the motor buttoned up.

Still should clean up the inside of the transfer ports to get everything nice and smooth.