where can I buy a 1mm base plate??
- Thread starter casper1981
- Start date
Blaner
Your Friendly South African Ambassador
improves port timing and puts into specs more suited for performance.
i have the CAD files for one if you want, you just need to take it to a laser cutting place and they will make it for you. PM me if you want the files
i have the CAD files for one if you want, you just need to take it to a laser cutting place and they will make it for you. PM me if you want the files
Blaner
Your Friendly South African Ambassador
PORT DURATION ISSUES.
MacDizzy--"It became clear to me after running some numbers through the two-stroke software I'm evaluating for the other part of this article that I could obtain the target HP value I was shooting for by using a combination of a 1 mm thick aluminum base plate spacer and its required additional base gasket. This raises the barrel a total of 1.5 mm. Not only would it let the transfer ports become fully uncovered and increasing their time area, it would allow the piston edge to be completely below the exhaust port when it was at BDC. I never like it when a piston is always exposed to the hot exhaust gasses - never having a chance to get out of the hot exhaust stream to cool off like it should. It seems that even a small adjustment here could mean the difference between detonating and not. Designing the engine this way requires milling the deck of the barrel to compensate for the base plate spacer setup. Decking was already going to be done since I previously discovered the squish thickness was far too thick for good throttle response but now I can calculate exactly how much to remove because I know what the final port timing specs are going to be. "
THIS ENGINES PORT TIMING HAS BEEN DETERMINED AS BEING:
STOCK BLASTER:
EXHAUST PORT:
OPENS: 91.5 degrees (33 mm below deck height) ATDC
DURATION: 177 degrees
TRANSFER PORT:
OPENS: 119.5 degrees ATDC
DURATION : 121 degrees.
BOOST PORT
OPENS: 125 degrees ATDC
DURATION: 110 degrees.
The Blowdown is 28 degrees of crankshaft rotation (figured from Exhaust port opening until first transfer port opens).
WITH 1MM BASE PLATE SPACER ADDED
EXHAUST PORT:
OPENS: 88.5 degrees (33 mm) ATDC
DURATION: 183 degrees
TRANSFER PORT:
OPENS: 116.5 degrees ATDC
DURATION : 127 degrees.
BOOST PORT
OPENS: 128 degrees ATDC
DURATION: 116 degrees.
Graham Bells Performance Tuning Specifications,
EXHAUST DURATION:
NOTE: a 200cc motor is not included on his list but if you look, a raised barrel will put the duration specs (183degrees) well within range of a good setting, ie between a 175 and a 250 as opposed to 177degrees which according to the list is what a 1x400cc 2stroke needs....The same problem is found with all the ports, they are set to what would be a good setting for a 400cc 2stroke, well out of range of a high performance 200cc!
DISPLACEMENT RIDING STYLE RPM EX PORT DURATION ̊
175 Enduro 9000 184-186
175 Enduro 9500 186-188
250 Enduro 8000 180-182
400 Enduro 7000 175-177
you will notice the stock blaster has a exhaust duration that is right for a 400cc enduro bike, a far cry from the needed 180-188. if you use a 1mm base plate, the durationg becomes 183, much better!
MacDizzy--"It became clear to me after running some numbers through the two-stroke software I'm evaluating for the other part of this article that I could obtain the target HP value I was shooting for by using a combination of a 1 mm thick aluminum base plate spacer and its required additional base gasket. This raises the barrel a total of 1.5 mm. Not only would it let the transfer ports become fully uncovered and increasing their time area, it would allow the piston edge to be completely below the exhaust port when it was at BDC. I never like it when a piston is always exposed to the hot exhaust gasses - never having a chance to get out of the hot exhaust stream to cool off like it should. It seems that even a small adjustment here could mean the difference between detonating and not. Designing the engine this way requires milling the deck of the barrel to compensate for the base plate spacer setup. Decking was already going to be done since I previously discovered the squish thickness was far too thick for good throttle response but now I can calculate exactly how much to remove because I know what the final port timing specs are going to be. "
THIS ENGINES PORT TIMING HAS BEEN DETERMINED AS BEING:
STOCK BLASTER:
EXHAUST PORT:
OPENS: 91.5 degrees (33 mm below deck height) ATDC
DURATION: 177 degrees
TRANSFER PORT:
OPENS: 119.5 degrees ATDC
DURATION : 121 degrees.
BOOST PORT
OPENS: 125 degrees ATDC
DURATION: 110 degrees.
The Blowdown is 28 degrees of crankshaft rotation (figured from Exhaust port opening until first transfer port opens).
WITH 1MM BASE PLATE SPACER ADDED
EXHAUST PORT:
OPENS: 88.5 degrees (33 mm) ATDC
DURATION: 183 degrees
TRANSFER PORT:
OPENS: 116.5 degrees ATDC
DURATION : 127 degrees.
BOOST PORT
OPENS: 128 degrees ATDC
DURATION: 116 degrees.
Graham Bells Performance Tuning Specifications,
EXHAUST DURATION:
NOTE: a 200cc motor is not included on his list but if you look, a raised barrel will put the duration specs (183degrees) well within range of a good setting, ie between a 175 and a 250 as opposed to 177degrees which according to the list is what a 1x400cc 2stroke needs....The same problem is found with all the ports, they are set to what would be a good setting for a 400cc 2stroke, well out of range of a high performance 200cc!
DISPLACEMENT RIDING STYLE RPM EX PORT DURATION ̊
175 Enduro 9000 184-186
175 Enduro 9500 186-188
250 Enduro 8000 180-182
400 Enduro 7000 175-177
you will notice the stock blaster has a exhaust duration that is right for a 400cc enduro bike, a far cry from the needed 180-188. if you use a 1mm base plate, the durationg becomes 183, much better!
Wait so you change some of the port timings by raising it up then you mill the head to compensate for the raise in the head? If this is so beneficial why don't more people do it?
cutting the head dosent change port timing at all, milling the head is just a easy way to gain some compression.
what i meant was that when you raised the cylinder 1mm the head would be raised too. lowering compression so you would need to mill the head to gain that compression back
Blaner
Your Friendly South African Ambassador
well you need to compentsate with removing material from the top of the barrel. the amount can be exactly the amount you raised it by, 1.5mm in this case (with extra gasket) or you can skim more to correct the deck beyond getting it back to standard. this will then help when it comes to having the head rechambered to correct the poor squish design of tha blasters.
and yes, raising the barrel most definately changes port timing, i think alot of people dont so either because they dont know about it or they are afraid of airleaks with the eaxtra gasket. i run this setup and have never had a airleak. the advantages include not only improving/correcting port timing but also the piston crown is lowered to exactly in line with the transfers and a touch below the exhaust where before the crown partially blocked the transfers and exhaust at BTDC, this is not good because the piston is always in the path of hot exhaust gas trying to escape, thus the piston never gets a chance to cool as it should.
if you want more specs in a more readable format, PM me and il send you some .doc files that i made up while working out the measurements and timing specs.
as far as im concerned, its a great thing to do, i believe Yamaha made the blaster like this with bad timing in order to keep the power delivery "tame" for beginner riders, remember blasters were entry level bikes...
and yes, raising the barrel most definately changes port timing, i think alot of people dont so either because they dont know about it or they are afraid of airleaks with the eaxtra gasket. i run this setup and have never had a airleak. the advantages include not only improving/correcting port timing but also the piston crown is lowered to exactly in line with the transfers and a touch below the exhaust where before the crown partially blocked the transfers and exhaust at BTDC, this is not good because the piston is always in the path of hot exhaust gas trying to escape, thus the piston never gets a chance to cool as it should.
if you want more specs in a more readable format, PM me and il send you some .doc files that i made up while working out the measurements and timing specs.
as far as im concerned, its a great thing to do, i believe Yamaha made the blaster like this with bad timing in order to keep the power delivery "tame" for beginner riders, remember blasters were entry level bikes...
Blaner
Your Friendly South African Ambassador
Not really hey, those figures i posted are including an extra gasket, here are the calculations i used to work it all out, most of you probably wont read it but maybe it will help someone understand this better.
I did the spacer at the same time as i did my head rechambering so it goes hand in hand. its a good thing to do all at the same time. i based all my thoughts on Mcdizzy's build and info,as well as reference to Graham Bells tuning book for squish thickness and port timing but with my own measurements factored in.
YFS BLASTER 200 CYLINDER HEAD MODIFICATIONS:
GRAHAM BELLS SPECS
TABLE 2.1 Minimum squish clearances
Cylinder size (cc) Clearance (mm)
50-80------- 0.6-0.8mm
100-125 -----0.7-0.9mm
175-250 -----1.0-1.4mm Blaster will fall in this category, eg 1.1mm
300-500 -----1.1-1.5mm
**Stock Blasters have a squish clearance of 2.63mm and 1.88mm on exhaust side and intake side respectively.
CALCULATIONS:
•Original deck height (0.5mm base gasket incl):
-0.63mm
•Deck Height After 1mm Spacer and Extra BASE Gasket 0.5mm:
New D.H = Orig D.H + Spacer + Extra gasket
0.63 + 1.0 + 0.5 = -2.13mm (below deck)
New total deck height + HEAD gasket (0.82mm uncompressed, 0.80mm compressed)
New Deck Height: 2.13mm + 0.82mm = 2.95mm Below Deck)
•Squish Band Thickness:
ORIGINAL HEAD SQUISH : LHS: 1.2mm
RHS: 0.45mm
GASKET : 0.80mm (flat)not included.
THEREFORE TOTAL ORIGINAL SQUISH THICKNESS:
Head squish + H.Gasket + OLD Deck Height
LHS: 1.2mm + 0.8mm + 0.63mm = 2.63mm
RHS: 0.45mm + 0.8mm + 0.63mm = 1.88mm
SQUISH THICKNESS: ORIGINAL HEAD WITH RAISED BARREL:
Head squish + H.Gasket + NEW Deck Height
LHS: 1.2mm + 0.8mm + 2.13 = 4.13mm
RHS: 0.45mm + 0.8mm + 2.13mm = 3.38mm
• Required Squish Band Thickness:
1.1mm (LHS and RHS)
THEREFORE: Required Skim Thickenesses:
DECK HEIGHT:
2.95mm – 1.1mm + TOLERANCE ( 0.10mm) = 1.75mm TO BE CUT OFF BARREL
THEREFORE NEW DECK HEIGHT: 2.95mm* – 1.75mm = -1.2mm below deck
2.95= 2.13+0.80 (GASKET INCLUDED!)
• Squish Band Thickness Original Head with Raised barrel and new CUT deck Height of 1.2mm: GASKET Incl.(see above)
LHS: 1.2mm + 1.2mm = 2.4mm
RHS: 1.2mm + 0.45mm = 1.65mm
•Amount to be Cut off Head to Equal Required Squish band of 1.1mm:
Barrel deck + gasket + original squish band – required Squish = amount to be cut.
LHS: 2.4mm – 1.1mm = 1.3mm
RHS: 1.65mm – 1.1mm = 0.55mm
FINAL FIGURES TO BE CUT:
BARREL: 1.75mm
HEAD: LHS: 1.3mm
RHS: 0.55mm
RECAP:
TARGET:
1.1mm squish band.
1.1mm = 0.8mm + 0.3mm (Target = H. Gasket + New Deck Height)-NO STEP UP OR DOWN TO THE SQUISH BAND!
TARGET ACHIEVED BY:
Original Squish on Raised Barrel – Amount to be cut from head – Amount to be cut from Barrel= required Squish Target
LHS: 4.13mm – 1.3 - 1.75 = 1.08mm (squish area)
RHS: 3.38mm – 0.55mm – 1.75mm = 1.08mm (Squish area)
I did the spacer at the same time as i did my head rechambering so it goes hand in hand. its a good thing to do all at the same time. i based all my thoughts on Mcdizzy's build and info,as well as reference to Graham Bells tuning book for squish thickness and port timing but with my own measurements factored in.
YFS BLASTER 200 CYLINDER HEAD MODIFICATIONS:
GRAHAM BELLS SPECS
TABLE 2.1 Minimum squish clearances
Cylinder size (cc) Clearance (mm)
50-80------- 0.6-0.8mm
100-125 -----0.7-0.9mm
175-250 -----1.0-1.4mm Blaster will fall in this category, eg 1.1mm
300-500 -----1.1-1.5mm
**Stock Blasters have a squish clearance of 2.63mm and 1.88mm on exhaust side and intake side respectively.
CALCULATIONS:
•Original deck height (0.5mm base gasket incl):
-0.63mm
•Deck Height After 1mm Spacer and Extra BASE Gasket 0.5mm:
New D.H = Orig D.H + Spacer + Extra gasket
0.63 + 1.0 + 0.5 = -2.13mm (below deck)
New total deck height + HEAD gasket (0.82mm uncompressed, 0.80mm compressed)
New Deck Height: 2.13mm + 0.82mm = 2.95mm Below Deck)
•Squish Band Thickness:
ORIGINAL HEAD SQUISH : LHS: 1.2mm
RHS: 0.45mm
GASKET : 0.80mm (flat)not included.
THEREFORE TOTAL ORIGINAL SQUISH THICKNESS:
Head squish + H.Gasket + OLD Deck Height
LHS: 1.2mm + 0.8mm + 0.63mm = 2.63mm
RHS: 0.45mm + 0.8mm + 0.63mm = 1.88mm
SQUISH THICKNESS: ORIGINAL HEAD WITH RAISED BARREL:
Head squish + H.Gasket + NEW Deck Height
LHS: 1.2mm + 0.8mm + 2.13 = 4.13mm
RHS: 0.45mm + 0.8mm + 2.13mm = 3.38mm
• Required Squish Band Thickness:
1.1mm (LHS and RHS)
THEREFORE: Required Skim Thickenesses:
DECK HEIGHT:
2.95mm – 1.1mm + TOLERANCE ( 0.10mm) = 1.75mm TO BE CUT OFF BARREL
THEREFORE NEW DECK HEIGHT: 2.95mm* – 1.75mm = -1.2mm below deck
2.95= 2.13+0.80 (GASKET INCLUDED!)
• Squish Band Thickness Original Head with Raised barrel and new CUT deck Height of 1.2mm: GASKET Incl.(see above)
LHS: 1.2mm + 1.2mm = 2.4mm
RHS: 1.2mm + 0.45mm = 1.65mm
•Amount to be Cut off Head to Equal Required Squish band of 1.1mm:
Barrel deck + gasket + original squish band – required Squish = amount to be cut.
LHS: 2.4mm – 1.1mm = 1.3mm
RHS: 1.65mm – 1.1mm = 0.55mm
FINAL FIGURES TO BE CUT:
BARREL: 1.75mm
HEAD: LHS: 1.3mm
RHS: 0.55mm
RECAP:
TARGET:
1.1mm squish band.
1.1mm = 0.8mm + 0.3mm (Target = H. Gasket + New Deck Height)-NO STEP UP OR DOWN TO THE SQUISH BAND!
TARGET ACHIEVED BY:
Original Squish on Raised Barrel – Amount to be cut from head – Amount to be cut from Barrel= required Squish Target
LHS: 4.13mm – 1.3 - 1.75 = 1.08mm (squish area)
RHS: 3.38mm – 0.55mm – 1.75mm = 1.08mm (Squish area)
bravo!
GREENZ for the mathz!!!!!
If you are not doing the head and base gaskets at the same time though, Chutzell is right, you need a thinner than 1mm spacer to account for the gasket thicknesses. The transfer floor are almost exactly 1mm too low so if you only want to raise the cylinder 1mm, you have to account for the gaskets.
GREENZ for the mathz!!!!!
If you are not doing the head and base gaskets at the same time though, Chutzell is right, you need a thinner than 1mm spacer to account for the gasket thicknesses. The transfer floor are almost exactly 1mm too low so if you only want to raise the cylinder 1mm, you have to account for the gaskets.
Blaner
Your Friendly South African Ambassador
rather that your motor exploding cause you were too lazy to work it out!
yes, Sicivic, if you just raise the barrel, it is a different story. but you can still skim off the top to get your deck height back to STD or better, thus making your squish smaller. i run with 1mm and an extra gasket and the transfers are perfect. pity i dont have any of my own pics.
