Temple for the tuners?

[mj43]

Dan

Plugs are only to stop shorting I am not sure 3xv ports overlap like Aprilia or KR

[maccas]

Mark,

You are correct, i will have to check.

Cheers,

Dan

[mj43]

Cheers Dan will have a beer and a think

Ok had a few beers ....

26.5 is where I set my KIPs ports at. 27.5 is where I set my main at. That setup with stock ignition works well with the Lomas pipes - actually they came alive with more advanced exhaust timing - compared with stock. Transfers at 38.5 is about where mine are. Your kips ports and transfers are a lot narrower than mine.

Crankcase flowing has always worked for me - see Bonneville results.

162 jets are very large compared with 152 to 155 that I ran on 35mm PWK.

Your head is probably higher compression than I run which coupled with the rich running might contribute to it cutting off early. Not running reed block inserts I expect to be a significant detractor from power.

Did you get an Air/ fuel meter on your runs?

[maccas]

Hi Mark,

Ok so my cylinder exhaust opening wise was pretty much the opposite but with narrower kips ports and narrower transfers.

Yep we had sniffer in the pipe on the runs and James said I could probably have come down a couple of jets. If my memory serves me correctly it was running about 12:1. So plenty safe. Head temp was in the high 60's even with the rich jetting.

I have ran it on the road with 155's with no issues and the plugs looked good.

Since the dyno I have done the following:

Fitted reed stuffers.
Bigger rad.
Fitted a stock standard head (fitted volume is now about 10.5cc with 1mm squish)
Lowered the barrel 0.4-0.5mm (the vertex pistons allowed me to do this as their compression height is higher than the KR piston)

So my transfers are now 39mm from the top of the cylinder.

Martin Johnson did some port work for me too, he widened the KIPS ports to 22mm (chord) and raised them to match the height of the main port. He also matched in the KIPS tunnels into the powervalves, I'd never had the tools to do it so there is no longer a step up from the tips tunnel into the powervalve.

So.... all my exhaust ports open at 27mm from the top of the cylinder.

I will take it down to the dyno again sometime soon. Would you like me to let you know when I'm popping down?

Cheers,

Dan

[mj43]

Yep pm me when you are going and I will pop over

[KR-1R]

KR250 EXdur (BBDC ABDC) ** SCAVdur (BBDC ABDC)
B. ........186 (93 93) ** 126 (63 63)
C. ........186 (93 93) ** 126 (63 63)
D. ........188 (94 94) ** 126 (63 63)

KX125 ........EXdur ** SCAVdur
90 (50.6) ......187 (93.5 ..) ** 131 (65.5 ..)
91(50.6) ....... lo187 hi191 (L93.5 H95.5) ** 131 (65.5 ..)
92 (54.5) .......lo172 hi189 ** 130
93 (54.5) .......lo172 hi190 ** 131

[mj43]

If you do the numbers I set the timing at

26.5mm ~ 94.2°
38.5mm ~ 65°

I have found that stock barrels can be up to a 1mm out on what they should be?

[maccas]

Mark,

Just out of interest I investigated the 3xv aux/gudgeon pin relationship:







Looks like it is an issue. This is with 3xv SP cylinders and pistons. I know I have marked where the piston pin bore is but it will still form a passage to the piston pin hole won't it as the pin isn't flush to the sides of the piston.

I was thinking. Could you not use a shorter pin and just put a thin (~1mm thick) 16mm disc of stainless in the end between the pin and the clip?

Danny mentioned that a wiseco KX pin is 44mm long versus the 46mm of the KR so that would leave room for two 1mm thick discs, one at each end. They wouldn't effect weight and they wouldn't come out because of the clips.

I wonder if the pin would wear against them at all?

Anyway just thinking out loud, I might try it next time I rebuild my 3xv.

Dan

[maccas]

Hmmm thinking about it the plugs could do to come out to as close to the side of the piston as possible as to prevent short circuiting from transfer to auxillary on the same side of the piston. Much like a large piston cut out causes. The plugs aprilia use look to try and come out as far as the sides of the piston don't they.

Dan

[mj43]

Dan

I like your idea. I had been trying to figure out how to keep the circlip, use a readily available piston pin and block off the hole.
If you modify your disc to a cotton reel, I think there might be enough room to fit it plus circlip.

I will post a sketch once I have drawn one up.

[TwoStroke Institute]

Thats the portmap from the cylinders used.



Stock kr1s pistons were in the bike.
Deck height is 0, piston at TDC is flush with the top of the barrel
Main exhaust is 26.5mm from top of the barrel which equates to 188.4 degrees duration.
Kips ports are 27.4mm from top of barrel which equates to 184.1 degrees duration.
Kips are 8mm high and 17mm wide (arc length).

Cylinder has an appaling lack of blowdown. Don't use plugs that delete the circlip. No plastic type products except for the expensive on can handle the heat. Plugs didn't gain even 0.1 of a HP when we tested them.

[mj43]

Dan

Piccy

Idea is to fit with the circlip, not sure how to get them off? Think it might need a small tapped hole in the centre so you can pull the plug at the same time as levering up the circlip? Dimensions are 1mm lip, 2mm gap, 0.2mm step then a 1mm high dome. Dia 16mm setp dia 13mm.

TSI - I am sure I read that Fritz or Jan reported a 2hp increase per cylinder when they fitted plugs. As the KR has more of a cross over than the Aprilia it might be expected that the plug may be of more benefit.

Piccy shows the pin plug overlaid on a stock barrel.
Shorting occurs from ~30° ATDC to ~62° ATDC
Looking at it on my barrels it may even short in to the B transfer


Barrel Cylinder cross section

[maccas]

Mark,

Yep that looks good to me!

I agree, you would need a way of getting them out and your solution sounds good. Once circlips are put in to the groove do they move at all? I mean if you fit a circlip and do a race or whatever, when you come to strip the top end have the circlips spun at all? Might be tricky getting to the end of the circlip if they spin in use if that makes sense?

Lozza,

I have tried to improve blowdown area by widening and raising the kips ports. By lowering the barrel I have gained 0.3 degrees of blowdown angle. I now have the kips ports and main opening at the same time, so I have effectively one very large port that will open simultaneously. The actually blowdown area is large but the blowdown angle may well be lacking yes. Only one way to find out really......

Dan

[maccas]

Cylinder has an appaling lack of blowdown. Don't use plugs that delete the circlip. No plastic type products except for the expensive on can handle the heat. Plugs didn't gain even 0.1 of a HP when we tested them.

Also Lozza, may I ask what you tested the plugs on? Was it a twin cylinder 250 or a single 125?

Cheers,

Dan

[TwoStroke Institute]

Tested on a 76HP Rotax that's won 4 or 5 Aussie titles and the last 5 Island Classic 250 classes(even gives the UK's best TZ350's hurry up around PI). Plugged pins showed no increase in hp/torque anywhere in the range. Ditto a h***a RS 125 and a KX65. I know it works as it does on a BRC kart engine and RSW/RSW, but I'm suspecting a certain threshold of performance level needs to be achieved before you will see a 1hp gain.
The main and subs opening at the same time is the worst option. Track, dyno and simulator tells us main open first followed by the subs 2-3deg later is the only way to go.