A simple but probably stupid question about engine work

[99LRDblaster]

So after some thinking, I was wondering something. Outside of base plate spacers, would there be any benefits with certain setups in machining some of the cylinder down itself to decrease port timing? Has anybody played with it or is this essentially a one way route and you don't want/need to?

 

[bagds101]

i dont know but i will tell you that how ken did my head mod, it is pretty close to the piston when it goes up. it is clese enough for my piston to push a screw into my head. so i think milling the cylinder might bring the piston even closer to the head. not positive but i am pretty sure. why not just advance or retard your timing?

 

[hudack]

i would imginne it would be like runing a stroker crank without a spacer plate or haveing the timing matched depending on how much you remove so i would say it would run like chit

 

[99LRDblaster]

i dont know but i will tell you that how ken did my head mod, it is pretty close to the piston when it goes up. it is clese enough for my piston to push a screw into my head. so i think milling the cylinder might bring the piston even closer to the head. not positive but i am pretty sure. why not just advance or retard your timing?

The head would have to be cut. It would be similar to a stroker setup without a spacer. This is exclusively a port timing mod and in general decreases port timing HOWEVER suppose you are running a stroker setup already and mill the base of the cylinder down and run a new head setup. You would decrease port timing, elongate the combustion cycle, and I was wondering if this setup could prove beneficial in any manner as it's been done before on other engines, although I know of nobody doing it on the Blaster.

 

[super noober]

The head would have to be cut. It would be similar to a stroker setup without a spacer. This is exclusively a port timing mod and in general decreases port timing HOWEVER suppose you are running a stroker setup already and mill the base of the cylinder down and run a new head setup. You would decrease port timing, elongate the combustion cycle, and I was wondering if this setup could prove beneficial in any manner as it's been done before on other engines, although I know of nobody doing it on the Blaster.

i belive that is how Wildcard does thier stroker setups, no plate, cut cylinder and head. keeps a stock appearance for all u cheaters out there hahahahaah jk jk

 

[slickerthanyou]

The head would have to be cut. It would be similar to a stroker setup without a spacer. This is exclusively a port timing mod and in general decreases port timing HOWEVER suppose you are running a stroker setup already and mill the base of the cylinder down and run a new head setup. You would decrease port timing, elongate the combustion cycle, and I was wondering if this setup could prove beneficial in any manner as it's been done before on other engines, although I know of nobody doing it on the Blaster.

I am not running a plate at all on my +3. You would have to talk to Ken as i don't remember what he did to my motor now...

 

[Blaner]

if you not running a spacer with a stroker and instead mill the top of the barrel, you are decreasing your effective compression, your compression on a 2stroke only begins when your exhaust port closes, 33mm on a stock jug (may be 31mm, not sure) from the top, so basically your stock motor has the compression : pi x r2 x h = pi x 3.3 x 3.3 = 112.28cc so if you decrease the height from the top of the cylinder to the top of the exhaust port, your effective comp becomes less, as it is, a blaster actually has the compression of a 112.28cc bike, now there is a point to argue with your 4stroke buddies! milling the barrel at the top a lot will actually make you technical motor "size" less!

The only reason i believe the barrel should be skimmed is to correct deck height to about 0.63mm below deck, but only involving a minimal amount of material removal, enough to get your port timing in spec with a 200cc, which a stock blaster is not.

 

[99LRDblaster]

if you not running a spacer with a stroker and instead mill the top of the barrel, you are decreasing your effective compression, your compression on a 2stroke only begins when your exhaust port closes, 33mm on a stock jug (may be 31mm, not sure) from the top, so basically your stock motor has the compression : pi x r2 x h = pi x 3.3 x 3.3 = 112.28cc so if you decrease the height from the top of the cylinder to the top of the exhaust port, your effective comp becomes less, as it is, a blaster actually has the compression of a 112.28cc bike, now there is a point to argue with your 4stroke buddies! milling the barrel at the top a lot will actually make you technical motor "size" less!

The only reason i believe the barrel should be skimmed is to correct deck height to about 0.63mm below deck, but only involving a minimal amount of material removal, enough to get your port timing in spec with a 200cc, which a stock blaster is not.

I'm speaking of milling the BOTTOM of the cylinder between the case and cylinder.

 

[Blaner]

I'm speaking of milling the BOTTOM of the cylinder between the case and cylinder.

Ahh, apologies...didnt pick that up, well i cant think of any advantages off hand...i dont see a point to it, you only going to retard your port timing and thats not going to help anything with a stock setup or with a stroker setup (which would make it worse) only thing i can think of is that you would improve your compression as you are now reducing your deck height without skimming. but its a trade off between very bad port timing and a little bit of extra compression, i dont think the extra comp can be weighed against the losses in port timing. you will have extra comp but it wont be usable.

hope i got it right this time....

 

[99LRDblaster]

Ahh, apologies...didnt pick that up, well i cant think of any advantages off hand...i dont see a point to it, you only going to retard your port timing and thats not going to help anything with a stock setup or with a stroker setup (which would make it worse) only thing i can think of is that you would improve your compression as you are now reducing your deck height without skimming. but its a trade off between very bad port timing and a little bit of extra compression, i dont think the extra comp can be weighed against the losses in port timing. you will have extra comp but it wont be usable.

hope i got it right this time....

True........however could you alter a the porting after the fact to negate the disadvantages of certain port timing setups? For example, the transfers on a stock stroke are not completely uncovered, however, with +4 stroker, the piston crown is what?..1mm below the transfers? You could do one of two things.....reshape the transfer ports and enlarge them 1mm below or mill the cylinder BASE down 1mm(or 0.5mm and do both). Gain?.....port timing is reduced enough to allow for added compression(if you so choose to) and combustion cycle(closed port phase), while still retaining the same basic port philosophy........granted you would have to port it COMPLETELY differently from what we are accustomed too.......just like normal stroker setups are ported differently. It would allow you to play with porting above and below port surfaces. You could in a sense, raise ports more(I would think) than a "normal" cylinder.

 

[Larry's Shee]

Problem with threads like this is that it makes my brain hurt :-/ . Only app for a stock cyl I see is if you raised ports to high and tried to correct it (or bought drag ported). If I understand correctly the transfers are still partly covered by piston at BDC, if anything I would raise cyl and mill the top.

Good thought provoking thread non the less. I:I

 

[Blaner]

i follow your logic, you have a point i guess it could work...best idea here is to get a pen and paper and a calculator and get to work, mathematics can answer almost all problems

 

[Blaner]

i will be investigating some sums with regard to porting for a +3 cause im planning on getting one sometime, so il tackle this when im busy with that...whenever that will be!

 

[99LRDblaster]

i will be investigating some sums with regard to porting for a +3 cause im planning on getting one sometime, so il tackle this when im busy with that...whenever that will be!

Are you a math major?

I'm alright at math, but it's not my forte. Anything past basic calc start making me do too much of this----> :-/

It's kind of like the difference between physics and quantum physics theory.

 

[Blaner]

haha no not really, i didnt do too well at it at school but i had to take it at university with my Bsc Geosciences so i kinda broke my mental barrier there, i enjoy it when its practical, like in engines! and when minerals crystallize out of magma of course

 

[99LRDblaster]

haha no not really, i didnt do too well at it at school but i had to take it at university with my Bsc Geosciences so i kinda broke my mental barrier there, i enjoy it when its practical, like in engines! and when minerals crystallize out of magma of course

Touche. I can go with that. I:I

 

[N8tsNastyBlasty]

shaving the bottom would reduce deck height and increase comp. leaving the stock porting and doing this would make the engine tamer and in essence detune the engine. thats what yamaha did when they designed it. they used low port timing to deliver a "tractable" powerband. its pretty flat and smooth stock. very predictable and just like the port timing RETARDED & slow . they do live longer like this because they dont have enough power to break. If you left the port timing low and then widend the ports with all of the usual porting techniques you would end up with a crap load of bottom end and mid range but the top end power would be sacrificed

 

[Kgibson]

I didnt read all the post, but i will say that how kennedy did the one he sent me. The piston came out the top several thousand. I ride the quad before Jordan when changes are made so I know whats up. And Kennedys motor was a PIG the worst out of 5 I tried last year

 

[Paulie B]

I'd do it to a cub for trail riding but not a Blaster.
Since the advent of the Serval, I wouldn't do it to a cub either haha

 

[blasterracer817]

a reason to mill the bottom of the jug with a stroker would be to drop the ehast port to piston hight so they are flush not a little lip. same reason people use a 1mm plate ona stock jug to raise the exhaust flush to the piston to get the most out of the exhaust port.