engineering squish heads

[Vintageman]

for that cost what is your expectations in power gain and /or is this simply necessary for you have porting mods and higher compression in mind.

I mean if just squish head versus stock domed head what is gained by that mod alone. Sorry for ignorance. Maybe it is a significant HP mod in its own right.

[srech77]

Hey guys - here is a link to some photos I threw up showing the new squish heads, and a couple shots of the bike, still incomplete, but RUNNING!

http://s1091.photobucket.com/user/sterl ... t=3&page=1" onclick="window.open(this.href);return false;

[srech77]

for that cost what is your expectations in power gain and /or is this simply necessary for you have porting mods and higher compression in mind.

I mean if just squish head versus stock domed head what is gained by that mod alone. Sorry for ignorance. Maybe it is a significant HP mod in its own right.

It's a fair question vintageman. I am not an expert on modern 2-stroke engine technology, but I am learning as I go. The primary two benefits (and someone can correct me if I'm wrong) of squish chambers is a more efficient burn, and makes it less prone to detonation. If you consider that the compression ratio on this bike now is approximately 12.88:1, that can lead to significant power gains, but also a higher risk for pinging and detonation if everything isn't just right.

Squish chambers puts modern 2-stroke technology on a vintage bike, and ultimately makes it more reliable, and more efficient. The spark plug offset and wide-open dome design of the vintage heads is fairly solid, but also primitive in its design. The combustion process gets shoved to one side, and the flame process loses efficiency. Centering the spark plug and squishing the heads makes everything tighter and allows the engine to utilize more air/fuel per cycle than the vintage heads do. This, coupled with the larger carbs, performance exhaust chambers, porting, UNIs, etc... makes for an engine that produces more power, more efficiently, at every rpm range.

And while I haven't road tested it yet, I have had it running in my garage, and the difference in sound and smoothness is substantial over the stock setup!

[srech77]

If you want a better, more thorough explanation of squish bands for the T500, check out this page ... very well-written piece by Glen Morgan.

http://www.ozebook.com/compendium/t500_ ... n/head.htm" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

And if it's hard numbers you're after (HP and torque gains) then I probably won't be of much help. I'm not building a race bike, just an aggressive cafe build. From other bikes that have similar modding, I can ballpark the figures at around 60hp (maybe more maybe less) when it's done ... considering the factory HP is around 47-50 depending on elevation and temperature, and extra 10 HP from a vintage motor is HUGE to me. I would never recoup the thousands I have into rebuilding this T500, but then again I will probably never sell it - these bikes become too special, and too rare, especially with this kind of work.

I just like the idea of bringing modern 2-stroke technology into the vintage bikes ... they run so much better.

[srech77]

1975 Suzuki T500 Titan Build
Motor
CBC1, DFL1, & PKSX™ Performance Coated piston and ring kit (.040” oversize) XS Cycle™ – Canada
Street Ported cylinders (bead blasted) (Eric – Sundial)
GT750 Intake Ports
Cometic™ copper head gaskets - .020” (annealed and coated with Permatex)
Squish cylinder heads at .040” squish clearance (centered plugs) + ½” cooling fin holes (RK Tek™)
Mikuni™ VM34 Carburetors with UFOs™
Uni™ 2-stage angled pods – 6 inch
Polished cylinder bolts and head studs
Jemco™ chambers w/ removable baffles (nickel-plated) Jon Easton
Factory Rods with new SE bearings – factory spec crank
Chassis/Electronics
Legendary™ GPS Tach/Speedo combo w/ custom CNC aircraft grade bracket (LM)
Akront™ WM3 Alloy rear wheel w/ stainless spokes (XS650 – Netherlands)
SimSpeed Curved License Plate Bracket with custom tail light
Front and Rear fender chop
Titan Performance™ custom rearsets
Titan Performance™ billet chain guard
Titan Performance™ Mini signals
Titan Performance™ headlamp brackets
Titan Performance billet brake torque arm
Motion Pro™ custom length brake cable
Carbon Moto™ Fully adjustable alloy clips-ons
Custom matching café seat - triple chromed by Black Hills Plating(MSD – Eric Tran)
New NOS fuel tap with transparent blue lines
New fuel tank, oil tank, and side panel (with no-rust tank liner)
New side emblems
Polished wheels, hubs, and engine covers
Polished rear sprocket carrier
Stainless allen bolts on clutch, sprocket, and generator covers
New oil injection lines
Electronic Transistor Ignition™ (HondaMan Mark Paris)
New ignition coils NOS
Shorai™ Lithium Ion extreme lightweight battery
Shinko™ 712 tires, tubes and rim strips
EBC™ brake pads front and rear
New clutch cable
New brake and clutch levers
New brake cam, spacer, o-ring – rear
H4 halogen headlight conversion (yellow lens)
New rectifier and signal relay NOS
DID™ chain 530 non o-ring
JT sprockets™ (15F, 33R)
Original rear shocks
Painted frame – enamel gloss
NGK B8HS Plugs
NOS Power wire
NOS Battery cable
New NGK plug boots
GP hand grips

[Suzukidave]

All that tech and then " original rear shocks "

[srech77]

All that tech and then " original rear shocks "

Fair comment Dave ... if I were building a race bike, you could guarantee there would be some progressive 418s on there, or something of the like. However, I kind of love the original narrow forks, drum brake, and chrome coil shocks on the Titan ... they charm me for some reason. And it kind of helps preserve the vintage look. And I guess if they were in worse shape, I would probably swap them out, but I lucked out on that bike in that the suspension and some exterior parts were in great shape when I salvaged the bike (only had around 12xxx on it the day I picked it up), so I couldn't bring myself to get rid of them ... at least not yet

Cheers -

[tz375]

for that cost what is your expectations in power gain and /or is this simply necessary for you have porting mods and higher compression in mind.

I mean if just squish head versus stock domed head what is gained by that mod alone. Sorry for ignorance. Maybe it is a significant HP mod in its own right.

There are two dimensions to that question.

First, a squish type head creates more combustion chamber turbulence and smaller droplets leading to more complete combustion, faster pressure rise and lower emissions.

The other aspect is that a quiescent chamber is more prone to detonation at even moderate performance levels. A well designed squish head allows for higher combustion pressures and therefore more power.

[srech77]

for that cost what is your expectations in power gain and /or is this simply necessary for you have porting mods and higher compression in mind.

I mean if just squish head versus stock domed head what is gained by that mod alone. Sorry for ignorance. Maybe it is a significant HP mod in its own right.

There are two dimensions to that question.

First, a squish type head creates more combustion chamber turbulence and smaller droplets leading to more complete combustion, faster pressure rise and lower emissions.

The other aspect is that a quiescent chamber is more prone to detonation at even moderate performance levels. A well designed squish head allows for higher combustion pressures and therefore more power.

I'm definitely on board with tz375- that is the knowledge you will get from any of the experts on performance 2-stroke motors ... unfortunately I'm now trying to source some TR heads, because a small crack has developed near the plug hole on my new squish heads. I have read many times that the stock heads are prone to cracking at higher performance levels, and I guess now I'm a member of that club :/ I could be mad, but it's just the nature of these bikes I guess. It's my payoff for running 12.8:1 compression and using stock heads with squish bands ... probably bound to happens sooner or later.

I've found a kind gentlemen in Canada who builds and races the TR500 who has a ratty set he is willing to sell me now ... thicker and stronger than the factory heads, and I don't know if I've ever heard of a set of Crooks TR heads cracking - pricey, but they are the business when it comes to hotting up a T500.

More to come later ...

[Vintageman]

Yes you can increase compression but, think quiescent has better mileage unless the squish area under piston is real small. that fuel does not burn under there very well as I understand


I just ported my GT550 1.5mm on exhaust +/- That is I made them all 38mm. I was going for more and had head milled 0.035"

I tried the milled head with my mild porting. It would ping. To complicated things I also put new needle jet. The ones I had were too large O-9 versus O-6 now (O-5 stock).

Before I made port/head mods and when I was running stock exhaust it would ping just a little. When engine was stock and I added 3 into 3 chambers it pinged like crazy.

Needle jets were very pitted and I handed reamed to O-9 (only closest ream I could find). No more ping. 32-33 mpg if I tried for it


So when I was using 0-6 Needle Jets, 1.5mm Ex raise. 0.035" milled heads and now pinging a little what to do? First I raised needle one clip just a little ping left (fuel definitely help cool down top end)

Screw it, I put the stock head back on 1.5mm Ex port and my chambers, shinny new 0-6 needle jets, and left needle clip one rich over stock. No pinging at throttle position and any rpms. Cool day too.

With the 0.035" milled head I think I had noticed a little more power hit mid rpms . No top end difference between stock and milled head I can discern.

Squish head better for higher compression be it heads/chamber boost. It really is good insurance. In my case, just a little modification it does not really matter. Oh I run 87 Octane too. I hate gas pumps with only one hose. if you select higher octane you probably get 1/2 gal of 87 from previous guy. Gas stations far a part and mileage poor so I gas up when I get a chance

Good news is I went from about 32 mpg to 39 mpg with new needle jets and when 39 I was riding aggressive

The T305 I recently raised a full 2.0mm Ex I shaved the doomed head 0.020" chambers and 87 octane no ping. That bike is tuned hot with respect to my liking. I may try another 0.010 off head to get more mid and hope no pinging

Squish nice but costly... may be worth just as insurance!

[tz375]

Yes you can increase compression but, think quiescent has better mileage unless the squish area under piston is real small. that fuel does not burn under there very well as I understand

It's the opposite. A correct squish gap reduces the amount of unburned mixture waiting to detonate, so a squish head will usually make more power and use less fuel. A very wide, and ineffective, squish band will act much like a quiescent head in that the mixture tends to detonate or go unburned in the quench area.

[Vintageman]

Tz375,

You are most likely correct. As a money loosing hobby (combustion engines that is) somewhere I have understood that fuel under the squish band will not burn at spark time (whole point is to prevent ignition at far end), and if you have a large squish band area more fuel does not ignite at spark so poor use of it and thus fuel economy.

The key is to have the squish as tight as possible to minimize that area of un-ignited to ignited. The problem during mass production that squish area is large to account for tolerances and ratio ignited to un-ignited high. So if you want best performance you need to manual adjust it which I am sure tuners do. Still have a finite area

Domed/Quiescent heads do have a long way for flame front to travel. So ping problem if far ends ignite due to heat of compression and the front travel opposite direction front created by spark. But I always understood all fuel burns.

I am sure the smaller squish head ignition area does mean a more efficient combustion thus more power and better fuel economy. I just don't know the theory . So I will agree with you if the squish area is real small, and due to a l better burn there may be only little arguable difference about which get better fuel mileage and yes squish can may win out.

Any papers on this subject one can bone up on?

Clearly squish you can run higher compression, Don't get me wrong squish head better, but so far it's not a must have at that expense for the way i drive the old girls. I gave those examples for sure If had squish heads I would be able to see a little more power for I good run of few more thenths compression but, shortly limited to the fact it is too much of hassle to find high octane gas riding about the roads putting in a gallon to gallon an a half at a time to be sure I don't run out with the next 50-60 miles or so if I did not fill up when I had the chance

Don't get me wrong squish head better, just haven't convienced myself it is a must for my bikes without them (at that cost part way to another new toy) as I use them

Fun Stuff

[tz375]

Properly designed and machined squish heads are far superior to the alternative an all modern two strokes use them. The real mathematical advantage of a quiescent chamber is that it is spherical and a sphere has the lowest ratio of surface area to volume. For a given volume (compression ratio) a spherical shaped head will have the lowest surface are and will tend to absorb less heat than a larger are squish head. That can be a valid design decision.

My GT750 motor has a stock head with just a small amount machined off and generates 165psi which is way the wrong side of sensible, but it works.

Your understanding of the stagnant area of mixture is correct. A too large squish band is as bad as a quiescent chamber for detonation. It's not about minimizing the squish band thickness, but about optimizing it for the intended use. The parameter is MSV Mean Squish volume and that is calculated at peak revs and must fall within certain limits. Too high is not good and too low is not good either. Squish thickness, depth and angle all impact MSV.

There are references in AG Bell's book and Bimotion.se has some info that you can access and they have a great head design software package.

[diamondj]

All that tech and then " original rear shocks "

Fair comment Dave ... if I were building a race bike, you could guarantee there would be some progressive 418s on there, or something of the like. However, I kind of love the original narrow forks, drum brake, and chrome coil shocks on the Titan ... they charm me for some reason. And it kind of helps preserve the vintage look. And I guess if they were in worse shape, I would probably swap them out, but I lucked out on that bike in that the suspension and some exterior parts were in great shape when I salvaged the bike (only had around 12xxx on it the day I picked it up), so I couldn't bring myself to get rid of them ... at least not yet

Cheers -

Hope you don't take offense at this but those 39 year old shocks are 39 year old shocks. Even when new they were filled with cheaper oil and lasted about a year or two before wearing out. You can get a set of stock looking Hagons with chrome bodies and springs from Dave Quinn set up to your machine and rider weight:

http://www.davequinnmotorcycles.com/cgi ... HOCKS.html

plus some bronze swing-arm bushing will work wonders on your rear suspension.

[srech77]

All that tech and then " original rear shocks "

Fair comment Dave ... if I were building a race bike, you could guarantee there would be some progressive 418s on there, or something of the like. However, I kind of love the original narrow forks, drum brake, and chrome coil shocks on the Titan ... they charm me for some reason. And it kind of helps preserve the vintage look. And I guess if they were in worse shape, I would probably swap them out, but I lucked out on that bike in that the suspension and some exterior parts were in great shape when I salvaged the bike (only had around 12xxx on it the day I picked it up), so I couldn't bring myself to get rid of them ... at least not yet

Cheers -

Hope you don't take offense at this but those 39 year old shocks are 39 year old shocks. Even when new they were filled with cheaper oil and lasted about a year or two before wearing out. You can get a set of stock looking Hagons with chrome bodies and springs from Dave Quinn set up to your machine and rider weight:

http://www.davequinnmotorcycles.com/cgi ... HOCKS.html

plus some bronze swing-arm bushing will work wonders on your rear suspension.

You'll get no disagreements from me on any of that ... it's more about what the bank account allows at the time, and I'm still working on squaring away the motor for now. If you have a place that sells the bronze bushings, please let me know. I've never been able to find them to this day for the T500 ... but if I decide to strip the bike down this winter, I would love to be able to put some of those in the swingarm.

thanks - sr