Porting questions

[tfaith08]

best, I wish I'd done that before I got it back together. I'll be doing that on the next go.

My cylinder modifications were these:
-Boyesen ports
-Smoother taper to boost port on the roof
-Widened piston port windows
-Rounded divider between piston ports and boost port
-Knife edged transfer port bottoms
-Smoothed exhaust port to an even shape after the sleeve
-cleaned up port mismatches

Piston mods:
-Matched port windows: 2.4mm wider, 2.0mm higher, 2.8mm radius on all edges, retained factory shape overall
-Angled port windows away from the piston ports and angled the windows at the divider towards each other.
-Matched radius and shape to the transfer port bottoms
-Cut oil gallery in piston pin area at 10 and 2 o'clock positions when viewed from the side. This is right up against the bearing.
-Mirror polished piston top

Head mods:
-shaved .22mm from head (4 tubes of valve grinding compound and 3 hours of work )
-Mirror polished the dome

Other: Ported reed cage, UNI w/o airbox lid, FMF Fatty, oil injection blocked off

Review:

After the heat cycles with 24:1 Super Techni-plate and huge jets (bottom clip position and 290 main), I dropped a 280 in. After 4 tanks in 2 days, I removed the airbox lid and moved the needle to the 2nd from bottom position. On tank 7, I mixed Yamalube 2R at 32:1 and dropped to a 270 main with the needle in the middle position and had a perfect plug.

With me on it (210lbs and 6'2"), stock gearing and 20" RAZRs, it'll launch in 4th without a problem. It'll come up in any gear right up until it winds out. In high gear and well below the powerband, I can punch it and it gets sideways in every type of terrain except for dry pavement. Hell, it'll spin the tires in 2nd on pavement with very little coercion.

It's much stronger than any other blaster I've ever been on. I will be upping the gearing by AT LEAST 2 in front.

 

[jus_me]

Nice job!!

 

[best]

Ahhh, don't get me started about pistons... This is a piston experiment we tried:
Matching the center transfer port:

It was successful and made more power at this size, but we kept opening it up more to find where "too much" is. This size was pretty much the optimum.
Notice it is an old well worn piston?
This was done just before replacing the piston. Why waste a good piston or an opportunity to learn by throwing out an old one? That epoxied cylinder was on its last overbore, so if it failed, not a whole lot was lost. I am also a strong believer in doing one mod at a time to see the effect. These motors lend themselves to that ability. (This piston was not used in the epoxied motor)

I have seen too many cracked and broken blaster pistons to start taking much metal off the piston skirts so I left the bridge and sides close to stock, but like you, I did angle the ports to the center of the piston and matched all the sizes, angles and radii. I do like using smooth topped pistons rather than the rough cast but I have not been able to feel a real life difference in power output or longevity.

I prefer rounded transfer port dividers but shortening them effects the tune so I just clean them up. I think rounding is extremely important at the intake bridge. As for shaving the head, when I was experimenting I did it with an 8" bastard cut hand file. I could take 0.020" (about 0.5mm) off in less than 10 minutes including a sanding on glass. I took the squish down from 0.120" to 0.020" on the stock head in 0.020" increments to look for optimum. The stock head will not work well that close, we had to rechamber the head to this shape to get good results:

The water cooled head is a KTM torroidal chamber, whereas the top head is hemispherical. The head on the right is stock. My son and I also made a torroidal chambered head too. If you do not have a rechambered head you should consider one. Best bang for your buck. Will multiply the gains you have felt from your cylinder mods. I have to put a plug in for JoeAK47. His porting work and rechambered heads (not pictured here) are works of art. He did us up a matching cc set of toroidal and hemi heads for a direct power comparison.

Here is another rechambered head with hand shaving file marks visible:

How does all this stuff work? Well, we use a butt dyno similar to yours. We do back to back tests with my son and I each trying it to compare notes. We have some bench marks. We know what stock feels like, we have a 32hp stock DT200 engine Blaster and a nearly 50hp KTM powered Blaster for comparison. We have found it easy to get somewhere between the 32hp DT200 and the KTM power with some cylinder mods and a rechambered head.

To pull wheelies in 6th gear without pulling on the bars takes at least 30hp.

Steve

 

[jus_me]

Cant get enough of this stuff.. Lots of power gains for stuff you can do yourself for free. Well if you have the patience the right tools and can do math. But if not all free than most of it is. As far as the 2 head shapes you were talking about the hemi and the toroidal being the same cc's could you tell a difference between the 2? Also what was the fuel and carb size?

 

[Blaaster]

After the heat cycles with 24:1 Super Techni-plate and huge jets (bottom clip position and 290 main), I dropped a 280 in. After 4 tanks in 2 days, I removed the airbox lid and moved the needle to the 2nd from bottom position. On tank 7, I mixed Yamalube 2R at 32:1 and dropped to a 270 main with the needle in the middle position and had a perfect plug.

I am rather concerned about you main jet choice.

A FMF alone calls for a #260, with the mods stated I feel you should be up around #310 - #320.

I am interested on why you used a different oil ratio to break in the engine, you used a very unorthodox method of break in, could you please explain what benefits your method has.

It seems like a lot of unnecessary palaver to go through.

 

[best]

Cant get enough of this stuff.. Lots of power gains for stuff you can do yourself for free. Well if you have the patience the right tools and can do math. But if not all free than most of it is. As far as the 2 head shapes you were talking about the hemi and the toroidal being the same cc's could you tell a difference between the 2? Also what was the fuel and carb size?

Yes you can tell the difference between the 2 head shapes. Torroidal has much more low and mid-range torque, hemi is a top end screamer. Pump gas (supreme) and stock Blaster 26mm carb so far. Experimented with 32, 35 and 38mm carbs but no great gains.

Steve

 

[tfaith08]

I am rather concerned about you main jet choice.

A FMF alone calls for a #260, with the mods stated I feel you should be up around #310 - #320.

I am interested on why you used a different oil ratio to break in the engine, you used a very unorthodox method of break in, could you please explain what benefits your method has.

It seems like a lot of unnecessary palaver to go through.

I thought it would require a much larger jet as well. It came with a 230 in it with the FMF and it was just a tad lean, so I figured "add 1.5 for no airbox lid, 2.5 for porting, .5 for reed cage porting" and I came up with 275 (280), so I threw a 290 in for the 24:1. I got everything up to a 320 main, but it ended up perfect with the 270. Everyone I tell says the same thing, but it's a nice coffee and creamer color. I did a half mile pull at WOT a few days ago and did a plug chop and it was spot on. Who knows?

As for the break in, I was a little concerned that I didn't apply enough oil during assembly (sort of a "what if I forgot something? thing) so I used the Techni-Plate because it was sitting around and I knew I'd be running it every day. I went through that many tanks because I was being cautious and frankly, I didn't know what I was doing so I took it slow.

Side note here: My dad called Klotz to ask about oil. He asked about the Techni-Plate and the guy cut him off and said, "If you don't run it every single day, don't use it; it'll make your cylinders rust after about 48 hours of no running. Use R50." I was kind of iffy about it, but hey, he works for Klotz.

So I used the Techni-Plate.

jus_me, to be honest, most of this stuff is free if you have the tools sitting around. I didn't. Dremel was about $100, carbide bits were around $9/ea. (x5), wire wheel bits are $8/ea. (x3), drill and drill bits were around $90, valve grinding compound was $7/pack +$5 for a window pane to use it on, carb cleaner $4.50/ea (x6), cylinder hone tool for when the shop doesn't do it right the fist time was $30, tape to seal up the crankcase while it sits around $6/roll, gasket remover compound that rusts your cylinder and barely works is $9/tube, acetone and pantyhose the get the metal shavings off of your arm is around $5, batteries for the digital torque wrench were $8 plus 2 hours in driving time to find them... it adds up faster than you'd like. However, once you have everything, it's much easier the second time around.

When people say you can rebuild a 2-stroke for $150, they already have the tools and everything else necessary and don't do anything other than the necessary. Between buying all the small things and parts, I came out just over $600 for everything. The second go will be closer to $200. But hey, if I'd kept all of my tools when I was in a financial bind, I'd have been set, now wouldn't I?

 

[tfaith08]

TBH, Blaaster, I think something is awry. I just looked around at other setups and mine is running the smallest main by far. More to follow.

 

[jus_me]

You have a valid point about how much it "actually" costs considering you do need the tools and not only that but you need the time as well..

As far as your jetting. Every bike is different. I would do another plug chop just to be certain..