Gasgasogeros
New member
hi on my gasgas ec300 the piston its not openull the sub ports by 4 mm with cylinder gasket 0,15 is normal this, or its must make a gasket 4 mm to open the subs ports?
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ec 300 sub port
- Thread starter Gasgasogeros
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widebear
Banned
As a general rule of thumb for raising transfers.If the design has them opening @ 118deg ATDC with an exhaust set @ 88deg ATDC,This would be suited for "enduro" type power- wide torque .Most euro bikes have this set up.
If you raise the opening timing to lets say 116deg and leave the exhaust alone the power will be even flatter on top with a moderate gain from 3500 rpm -5600 rpm.If you raise the exhaust and transfer timing to lets say 84 deg and 116 deg then a slightly narrower power band with a much higher rpm peak is the result
If the transfers are too big or too small to begin with then cylinder filling capibilities are a big problem.These issues influence the power output the most.
As with most 2 cycle designs go ,the many comprimises that have to be made so most people can ride them can cause a good bike to be a pile once it hits the dealers so keep in mind that relative small internal changes might show no gains or loses at all.
There are many SEA papers written to clarify this.
And as many ways to skin the same cat.
Keep in mind the easiest way to raise ports is with gaskets
If you raise the opening timing to lets say 116deg and leave the exhaust alone the power will be even flatter on top with a moderate gain from 3500 rpm -5600 rpm.If you raise the exhaust and transfer timing to lets say 84 deg and 116 deg then a slightly narrower power band with a much higher rpm peak is the result
If the transfers are too big or too small to begin with then cylinder filling capibilities are a big problem.These issues influence the power output the most.
As with most 2 cycle designs go ,the many comprimises that have to be made so most people can ride them can cause a good bike to be a pile once it hits the dealers so keep in mind that relative small internal changes might show no gains or loses at all.
There are many SEA papers written to clarify this.
And as many ways to skin the same cat.
Keep in mind the easiest way to raise ports is with gaskets
Gasgasogeros
New member
After the case mods
Now i know why the gasgas dont make respect horsepower bad port disegn end bad case casting
With the piston at top dead center, how far down is it from the top of the cylinder?
The transfer port gasses are pressurized, so some mismatching might be a non-issue. By the time the piston has reached bottom dead center, the gas mixture would have already been expelled anyway.
The transfer port gasses are pressurized, so some mismatching might be a non-issue. By the time the piston has reached bottom dead center, the gas mixture would have already been expelled anyway.
Gasgasogeros
New member
With the piston at top dead center, how far down is it from the top of the cylinder? About 3.8mm 
Gasgasogeros
New member
My question is this its comon on gasgas or something mistake on my bike ? because the piston is not oem but a vertex i know the heed must cutting on laxte the same as the gasket on base of cylinder
There is more than one mistake in play here because if you spaced the cyl further up to completely uncover the port you would end up with a lot less compression. If the piston deck to pin height was wrong and it was changed to uncover the port you would have so much less squish it may not even run.
I have seen casting flaws combined with the mass production machining tolerances being on the safe side to the extent that simply milling the parts to take away the excess safe factor results in big horsepower increases. This may be a case where unluckily all the parts were fudged on the safe side too add up to a big error end the end. I would be curious to know what the measurements would come out with a different cylinder in place.
widebear
Banned
I would'nt call the production tolerences mistakes. The bikes have more than enough power for the average rider and the 250's and especially the 300's seem to run very good with the cylinder lower rather than higher. The 200 is another story. Here are some pics of the preliminary port matching on a very strong running 200 I built.Notice how much expoxy was required on the one case half!
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If the factory leaves .120" piston to head and .060" is enough to insure that there is no problems than what would you call giving up compression which = free torque/horsepower. If a guy buys a 300 it should run like a 300 not a 200. Blueprinting an engine will only gain the amount of power that was lost in production tolerances vs. putting clearances on the money. In this case I'm not sure if the reason is for the question as to why is the piston not clearing the port and are they all like that or if it's part of a search for missing power.
widebear
Banned
On my 03 mc250 I expermented wirh raising the cylinder to ensure the exhaust port being fully open at bdc and then cutting the squish to make up for the lost compression, it ran like a turd with a much, much narrower power band with way less torque. I finally removed one of the base gaskets to where the comp was 200 psi and it ran much better but more like a jap two stroke motocrosser than a enduro bike .On my next 250 ec I just went to the thinnest base gasket and left the head alone, the compression again 200 psi. The result being a sweet torquey, flexable woods engine that stokes everyone who rides it. Certainly not as much peak horsepower or overev as the mc but a totaly rideable and flexable power source that gives the orange and berg riders lots to worry about. who'd a thought.
That makes sense to me since the critical part of the process is related to the upper edge of the port and the squish. When the piston is at the bottom it is no longer moving and the transfer port has already done it's job. Moving the upper edge changes timing and dynamic as well at static compression. If engines vary a lot from bike to bike it would back the reasoning to not copy your buddies jetting since his dynamic compression may not and probably doesn't duplicate yours.
widebear
Banned
{ quote If engines vary a lot from bike to bike it would back the reasoning to not copy your buddies jetting since his dynamic compression may not and probably doesn't duplicate yours.} unquote.
You make a very valid point there Lanky one. - The reason. which is why I have allways summarily dismissed the silver bullit jetting solutions being offered up by the bright and ambitious for mass consumption the lazy and inept.
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You make a very valid point there Lanky one. - The reason. which is why I have allways summarily dismissed the silver bullit jetting solutions being offered up by the bright and ambitious for mass consumption the lazy and inept.
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