[J-Madd]

BB Shearer's made a best of 103 hp (with Lectrons) @ 9000 rpm, with no overrev whatsoever. SBs made 103 (with Lectrons)@9600 rpms with good overrev. BBs had a little better power at lower RPMS, not a good broad curve that I thought the BBs produced.



We ended up getting 109 hp out of the SBs with some different carbs, but never tried the BBs with them.



So, is it better (in 300ft) to have a motor that makes 103hp @9000 or 9700? Or does it even matter as long as its geared accordingly? The motor should (and did) make peak power quicker (i.e. reach 9000 rpms quicker) with the BBs for sure, as the SBs had to rev out to 9600 rpms.



I plan on getting more HP out of this motor, but for now I have to run it for what it is.

 

[J-Madd]

HP is HP, more is good. Personally I have always liked more rpms. The low end on the BB is similar to the SB pipes, so why wouldnt you want to run the pipes that make more power? As long as you gear and clutch it correctly, it will run faster. Your never going to launch a Banshee at anything less than full throttle anyways, so low end isnt as much of an issue. Also remember that a pipe with more overrev will be a little more forgiving if you miss the shift on the high side a bit. The 10mil will have enough ooommmpphhh to pull it out. Just my .02

This is kinda what I was thinking.

Did you see if the BB pipes liked more timing or play with timing any? What carbs and what size made more power?

We tried the timing from +11.5 (plate maxed out) and +8 with the BBs. No significant difference at all on peak hp or the curves. We didn't overlay the graphs, but they looked about the same, and peak hp was same and at same rpm. Never tried to change the timing on the SBs - just left at +8.



We started with 41.5 mm (?) Lectrons with the needles (packards) set at 1.88" and pjs wide open and ran them all the way down to 1.5 turns out. Made the best power at about 2.5 turns out. 103 hp.



Next we went with PWKs. PWK 39 mms made the most power. The first set we tried was drilled out to 0.118 and also had a powerjet that accepts a mikuni pilot jet (in addition to the clippard pj.) We drilled out that jet to 0.70" for the second run and it was bout the the same - 105 hp I believe. These carbs were running it lean, even with the pj wide open.



Next we put on some more pwk 39mms that had been drilled to 0.120" with single clippard pjs wide open. First run was 109 hp. Made another run I think and it was 107 or so.

I never know what to think with these dyno testimonials. Matt at Shearer flat out told me that he re-designed the new SB OOF pipes specifically for the 421 - 4 mill cub motors. He said he's getting 5-7 HP more with the new design. He also said that for a 10mill cub he would recomend his SB OOF for draging and his BB OOF for duning. (BB would keep less heat in the motor for long run times) I never hear about guys making changes between parts. I'd want to hear about the timing and jetting changes for each pipe. If you don't find the best overall tune for each part you try...then your only finding out which pipe worked best for the jetting and timing you had for a baseline.

I'm not ripping anybody....I'm just saying....It would be nice to get ALL the notes from the dyno session. A/F ratio for runs, compare torque curves, peak power VS. overall power, etc......

But hey, thanks for sharing the info. It's better to get some real info than just a bunch of opinions.

Overall power was very similar among the different pipes. At least nothing really jumped out on the graphs as being different - again, we didn't overlay them. Don't remember the TQ exactly, but I'm sure the BB made more. We didn't use A/F ratio to tune. Just compared back to back runs to see which way the power and peak went; and tuned accordingly. I DON'T THINK THESE ARE THE NEW SB SHEARERS, BTW. I've had these about 3 years and I don't think those were out yet.

For a 300 foot race, I'd put on what makes the most HP and Torque the soonest.J...how much tuning did you do per pipe? Timing, jetting, etc?

Who ported the cub? I'd like to see a cub ported for SB and a cub ported for BB for an all out comparison...but I realize that will never happen.



Kevin @ HJR told me I should be running SB on my 10 cub, I'm just wasting any more money on pipes unless I had a concrete reason to...that'll show up as a number on a slip.

These cylinders were ordered from the builder knowing I intended to run the BB pipes. Your saying run the BBs? I guess I'll have to try both at the track and see which is better, but I'll have to calculate gearing for the 600 rpm peak difference. I won't name the builder; I think there is more in this motor. The domes were kinda jacked up. I had 200 psi and 180 psi in the left/right cylinders, respectively. The one with 200 had pitting when I took the head off, even though I never saw it on the plugs. The plugs are hard to read on the dyno, compared to the track. I have some new domes coming, I'll keep ya posted when I run it or dyno it again.

 

[J-Madd]

Stop talking smack about the Lectrons already J...LOL.

J/K.



Good research, like you said...the track numbers don't lie.

I hate relying on a dyno to be honest...it's cool to F around on, but too many a man left a dyno session with his head down thinking that number meant much...you know what I'm saying.

I think the new SB pipes have only been out a year or two at most.

Yeah I know its just a number, but my unported (cleaned up by F.A.S.T.)421 Cub made 98 hp with the pjs all the way out, then 100 hp on the next pull with 'em 1 turn in (We didn't do much more tuning on it after that). So for a drag ported 10 mil Cub to make only 109 (and tuned to lean to run at the track when it made that HP) is dissapointing.



There have been several smaller motors than mine make more power on this particular dyno.

 

[J-Madd]

Oh and I am gonna run the Lectrons on it for now. My friend and dyno owner/tuner said they would be much safer on it. They give it plenty of fuel across the board. The PWKS seemed to be a little lean everywhere - and if we did richen them up, the hp would probably go down to about the same as the Lectrons.



So to be fair to the Lectrons, had we got them in the same state of tune as the PWKS (ragged edge lean) they probably would have made similar HP.

 

[J-Madd]

Squish came up different everytime I checked it. I finally decided it was around 0.055". I got measurements as low as 0.49" in one cylinder a couple of times; but I got 0.055" several times. Piston rocking, I guess.



I have the domes and calipers in front of me. Squish band is 8.26 mm (0.325") if I'm measuring it right. It's the surface from the outside until it meets the inner combustion chamber right? Need any other measurements let me know.

 

[J-Madd]

Getting off subject now, I know, but here is the battered 200 psi dome.

 

[J-Madd]

wow the truth comes out. motor is questionable, carbs wern't in the similar state of tune.>.. now this post will start a war on which carbs are better and which pipes are better..



last 421 i did about 3-4 years ago had average domes from fast for a cub. and BB shear's and 41mm lectrons it did 105+ and pulled VERY hard also the carbs were having problems suppling enough fuel. james was going to get bigger bowls or possibly pump it. but ended up seling the motor due to funding issues'



so if your lec's are suppling more than enough fuel and you have the stock small bowls i;d say there is a LOT more left inthe engine. get the correct alky domes for it and try again.. the domes will make a big change in the motor..



motors that rev high are fun to ride BUT i always have found that to get my fat butt around i need the bottom end and aceleration capacity.





either way should be a fast engine!!

We got the Lectrons as lean as we comofortable with, it just happened that the PWKS were (too) lean when we bolted them on. I was already biased toward the PWKs, I admit it. But I didn't intentionally run the Lectrons out of tune to make them look bad.



Ever notice after a hard dyno pull that the plugs are always nearly dry with PWKs and wet with Lectrons? My friend says his motors last longer with Lectrons - we think this may be why. I dunno. Any opinions?

 

[J-Madd]

I was just teasing about the Lectrons J, you know that...



Really should measure squish with the domes on the motor.

high .040s to mid .050s is fine. I run mid to high 50s. I'm gonna cut that down a little and get low 50s for this year.

I need it to come out of the hole a little harder for my fat arse.



My plugs are normally a little wet when I come back off a run...I'm fine with that. I run a pump and big bowls, too. Overkill, but why fix what ain't broke!



It takes a couple passes to get heat on the plugs...



I run 20cc alky cut domes on mine J. I have a set from HJR and a set from Dan Wade @ Patriot.

Squish was measured with solder with head torqued down. My new domes will be 20 cc. These were 19 cc. And yeah, I know you were just kidding about the Lectrons. It was really toward cam - he's rubbing it in my face a little

. I've been hating on Lectrons for a long time, and he's seen that in posts here and on HQ. I have to admit I was wrong (and he is right) about some aspects of them

; but there is room for improvement in their design, I think.

 

[J-Madd]

Thanks for the input Travis.



Well, I got some new domes that were supposed to be less compression and ended up giving it 210 psi and 0.052" squish. I think the motor is positive deck, so the 20 cc domes don't actually come out to 20cc bolted on.



It ran 3.99 @80 first pass with me on it (185 lbs.) It ran 80.X mph 90% of passes regardless of 60 ft, or if it bogged or got sideways. Gearing is topped out, I think. One a good pass with a 1.45 60ft, I had to try 3 times to hit 5th, so it only went 75 mph and still ran 4.004. My 60ft and 150ft times were 0.07 seconds faster than any other pass, so I figure that to be a 3.92 pass if it would've shifted.



These were all passes with SB pipes. I am very pleased with this motor so far. Not the fastest 10 mil Cub out there, but it's consistent and fun and will probably get dialed (with better gearing) in the mid to low 3.90s and probably have a few .80s on a good pass.





I will compare back to back passes with BB pipes and keep ya'll posted.

 

[J-Madd]

Tried the "new" SB Shearer's along with a new, much better chassis. Ran best of 3.85 sec, 1.41 sec 60 ft. Consistent 3.86 to 3.91 e.t.s. all day long (183 lb rider). Don't know if I even want to try another pipe on it. Couldn't be happier with the motor/chassis combo I have now. Even with what seems to be strange specs (loose squish, lots of compression) this motor screams.

 

[J-Madd]

UPDATE: Ran back to back runs SB vs BB.



SB: [email protected] 80 mph 1.41 60ft.

BB: 3.89 @ 80 mph 1.41 60ft.



Clear as mud. lol. Sorry, don't have those time slips; but I do have these:



Best pass with BB. (Don't mind the reaction time - Damn staggered heads up tree gets me every time, lol)

Best pass with SB. Same track, different day, different tires and different track conditions. Not really apples to apples.

On another note, this motor/chassis combo runs about the same times at 3 very different tracks with only tire pressure adjustments. It even ran identical times (and mph) going from 72 r/o 14 staggereds to 76 r/o 14 staggereds with NO gearing change. Good 60 ft times are easier to obtain with the bigger tire, but not better (I had more 60 ft passes in 1.3s with the big tires, but still had some 1.3s with smaller tires).



To sum this thread up. I would say that the BBs are easier to get down the track being more forgiving. I can shift into 3rd gear quicker with the BBS without fear of falling out of the power. I believe with both pipes that I could have geared a tooth smaller in the back and ran even better if the 60 ft times would stay good. I am certain that the BBs would pull higher gear.

 

[J-Madd]

I think I'll have to take both sets of pipes with me to another track for another back to back pass. As of right now I prefer the (silenced) BBs on them, even though SBs look so much better, and mount easier to my chassis.

 

[J-Madd]

I also use an air density meter and monitor tire pressure before nearly every pass; noting how the 60 ft times correlate to the pressure for the given track conditions. Once you get the a/f dialed in by the meter, you rarely ever have to pull the plugs. IN fact I usually use the same plugs that were purged on from the previous race if the a/d is about the same. If it's way different, I'll put in a fresh set so I can get a new reading.

 

[J-Madd]

My limit is only 4 bikes at the track. Gets overwhelming after that (juggling jetting, pressure, gearing, etc.)

 

[J-Madd]

Thanks for the info. I wouldn't mind trying those. I have BB and SB CPIs I could try also. That's a lot of pipe swapping for the track, though; when it's probably just gonna run about the same. I really don't like lots of dyno runs, because the dyno seems to be harder on my engines than the track.