AE folks will love EK various bike pictures

CDHE said:
Here's my XR. XR750 heads and custom aluminum cylinders on a 1000cc lower end.
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Sweet! Did your xr cases let go on you hence the 1000 bottom end?

I have a N8's in my tracker and have had a set of 883 heads converted for the 1200. The heads and manifold will support around 120hp rear wheel but right now those pipes are killing me. I did a base line dyno pull with stock 1200 heads and N8's with a 165 main in a 42mm hsr and the pipes are holding it back real bad.

**** Edit- never mind...... 1000 bottom end = thumb starting ;)
 
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Ian Short said:
Sweet! Did your xr cases let go on you hence the 1000 bottom end?

I have a N8's in my tracker and have had a set of 883 heads converted for the 1200. The heads and manifold will support around 120hp rear wheel but right now those pipes are killing me. I did a base line dyno pull with stock 1200 heads and N8's with a 165 main in a 42mm hsr and the pipes are holding it back real bad.

**** Edit- never mind...... 1000 bottom end = thumb starting ;)
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I used an NOS XR1000 lower end that I bought on Ebay 20-odd years ago. Finished the bike, and was ready to fire and tune, then I got a wild hair and bought a basket case Laverda. Hope to get back on the XR this winter. Dry weight about 345lbs. With the parts I've got in it -Axtell cams, Jerry Branch manifolds, Cosworth pistons, flowed heads with big titanium valves, crankcase scrapers, etc- thinking that it might make 105HP?????
 
CDHE said:
I used an NOS XR1000 lower end that I bought on Ebay 20-odd years ago. Finished the bike, and was ready to fire and tune, then I got a wild hair and bought a basket case Laverda. Hope to get back on the XR this winter. Dry weight about 345lbs. With the parts I've got in it -Axtell cams, Jerry Branch manifolds, Cosworth pistons, flowed heads with big titanium valves, crankcase scrapers, etc- thinking that it might make 105HP?????
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I know from my conversations that a mini sump was used by many as well as a scrapper on the crank. Are you willing to share any of your flow numbers on the heads? Curious about your intake and exhaust flow at 50% cam lift and at full lift.

These are my 883 conversion heads and I'm flowing 145cfm at 0.500" lift on the intake... I'd have to check the flow sheet for the rest of the numbers. Using the 883 heads will give it a solid 0.250" squish band. We try and stay away from the titanium and stick to stainless and also keep the seat pressure as low as possible. (I've forgotten what I've been told my static and over the nose pressure is but I'm not using beehives)

My good friend is an absolute fanatic about maintaining/obtaining the proper rocker geometry as well.
 

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Ian Short said:
Iron head XR's were in the 82-83hp range at the rear wheel. The alloy XR's in the 90hp range and towards the end of the XR era in the 2000's there were quite a few that were in the 100hp range. A good friend of mine was there right from the beginning and has built and dyno'd many xr's. He used to road race his back in the 80's and 90's.

A flat track version of the XR750 weighed in at just under 300lbs.
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Correct... I remembered the 100 hp figure from "Harley Racers" by Alan Girdler, apparently I misinterpreted a statement, the 100 are quite clearly attributed to the later alloy versions. According to Dick O'Brian, the final iron engines made a healthy 80 rwhp. Awesome beasts!

Most definitely more than a cooking Lav twin, and more than many a triple btw.:ROFLMAO:

piet
 
Guess there are hardly limits if no holds are barred, but I was very surprised when I built the Moto Witt 883 Sportster Cup bikes in 1994-96.

We were bound to a very strict rule book, allowing virtually no mechanical changes to the engine, basically just careful assembly and setting up. Starting from the stock 44hp of the german market version, we ended up at 78-80 race ready (3 engines, every one ever so slightly different). The rules mandated stock pistons, valves, cams, followers, carb, ignition (but with a higher rev limit), a choice of 2 allowed air filters, alternator and starter remained in place. No porting allowed, only hint in the book was that the valve seat inserts were allowed to be flipped over... the big secret was to get the heads flowing properly at the valve seats. Exhaust was limited to 95dB, which proved to be a challenge at times!

Due to us coming runner-up in '95 and winning the german championship in '96 we were invited to Daytona and were consequently completely destroyed by the US young guns. Quite a few future WSB and GP kids were cutting their teeth in the class at the time! Chatting with the Barnett squad chief clearly showed in which areas we were lacking and despite loads of help from Scott "Z-man" Zampach (H-D Super Twins champ at the time) we didn't manage better than12th place in the '95 race. Was a steep learning curve and loads of fun though!!

Scott Zampach also rode the Tilley/Saxon Triumph in '95 while it was being maintained by Paul Taylor, who had also overseen the Laverda/Motodd/Saxon effort with Alan Cathcart.

piet
 
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sfcpiet said:
Guess there are hardly limits if no holds are barred, but I was very surprised when I built the Moto Witt 883 Sportster Cup bikes in 1994-96.

We were bound to a very strict rule book, allowing virtually no mechanical changes to the engine, basically just careful assembly and setting up. Starting from the stock 44hp of the german market version, we ended up at 78-80 race ready (3 engines, every one ever so slightly different). The rules mandated stock pistons, valves, cams, followers, carb, ignition (but with a higher rev limit), a choice of 2 allowed air filters, alternator and starter remained in place. No porting allowed, only hint in the book was that the valve seat inserts were allowed to be flipped over... the big secret was to get the heads flowing properly at the valve seats. Exhaust was limited to 95dB, which proved to be a challenge at times!

Due to us coming runner-up in '95 and winning the german championship in '96 we were invited to Daytona and were consequently completely destroyed by the US young guns. Quite a few future WSB and GP kids were cutting their teeth in the class at the time! Chatting with the Barnett squad chief clearly showed in which areas we were lacking and despite loads of help from Scott "Z-man" Zampach (H-D Super Twins champ at the time) we didn't manage better than12th place in the '95 race. Was a steep learning curve and loads of fun though!!

Scott Zampach also rode the Tilley/Saxon Triumph in '95 while it was being maintained by Paul Taylor, who had also overseen the Laverda/Motodd/Saxon effort with Alan Cathcart.

piet
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Here's a pic of a twin plugged 883 conversion head that was put on an 88ci Buell X1 race bike. These heads were capable of supporting 140-145hp at the rear wheel and 130-135tq. The second pic is my 883 conversion head beside Don's..... he did both sets of heads.

All stock sportster's are slow....... the 1200 moves at a galcial pace while the 883 moves at an evolutionary pace.

I also have never come across an engine that is as sensitive to exhaust systems as the 45* v-twin. The shared intake manifold is so short and the uneven and changing fire angle makes it vital to get the exhaust out and the new charge in the moment the intake valve leaves the seat.

The XR750 had very small ports, similar to a Norton 750, and relied on velocity to keep everything flowing. It seems to me that the triple Laverda's have some of that happening as well.

My understanding is that the XR750's don't really have any bottom end or mid range..... the trick is to get them wound out on the dirt ovals and that's where they start to shine. The four speed gearbox holds it back as well, there were a few 5 speed gear boxes made but they are rarer than hen's teeth and apparently rather delicate.
 

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Ian Short said:
I know from my conversations that a mini sump was used by many as well as a scrapper on the crank. Are you willing to share any of your flow numbers on the heads? Curious about your intake and exhaust flow at 50% cam lift and at full lift.

These are my 883 conversion heads and I'm flowing 145cfm at 0.500" lift on the intake... I'd have to check the flow sheet for the rest of the numbers. Using the 883 heads will give it a solid 0.250" squish band. We try and stay away from the titanium and stick to stainless and also keep the seat pressure as low as possible. (I've forgotten what I've been told my static and over the nose pressure is but I'm not using beehives)

My good friend is an absolute fanatic about maintaining/obtaining the proper rocker geometry as well.
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Ian, I don't have precise flow calcs, but I have (somewhere) info about the numbers Jerry Branch was shooting for when working on these heads. Will track it down and get back. Here's my then GF/now wife on my old bike with Buell Engine, N8's, 42mm HSR. Thing was a beast!
 

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CDHE said:
Ian, I don't have precise flow calcs, but I have (somewhere) info about the numbers Jerry Branch was shooting for when working on these heads. Will track it down and get back. Here's my then GF/now wife on my old bike with Buell Engine, N8's, 42mm HSR. Thing was a beast.
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I think you likely had the thunderstorm heads on it as well...... the n8's are a great cam and used to be a better deal than the n4's.

The XR750 heads are all about velocity..... you don't want to lose that. I'll see if Don still has his flow numbers and if he is willing to share. (He knew Jerry as well).
 

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Here's the article that I mentioned. Before and after flow, HP and torque are pretty remarkable. I have the all of the mods described in the article (with maybe 60cc less displacement) and a few others; mostly picked up from the (also attached) factory racing bulletin, along with 10.5:1 Cosworth pistons and degreed in cams from Axtell. Really looking forward to getting it on a dyno.
 

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CDHE said:
Here's the article that I mentioned. Before and after flow, HP and torque are pretty remarkable. I have the all of the mods described in the article (with maybe 60cc less displacement) and a few others; mostly picked up from the (also attached) factory racing bulletin, along with 10.5:1 Cosworth pistons and degreed in cams from Axtell. Really looking forward to getting it on a dyno.
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Funny you bring that up...... I was just texting a friend about that auction.

I think if you get it for around the $6-7k mark and you plan on keeping it, you've done not bad. It likely tied up a piston....... I think a budget of $3.5k would be fair to get it sorted properly maybe a bit more if you have to rebuild the crank.

With the Canadian dollar and taxes I'd need to get it at or less than the $3.5k mark in order to sort it and make some profit. The Canadian market is also much smaller and right now Canadians don't have seem to have much spare change after 10 years and counting of of a socialist gov't. The gov't around my home seems to be a bit of an autocracy and I'm not sure that the powers that be will have any empathy for a 7th motorcycle.

I think it offers a great opportunity for someone looking for a xr style tracker if they know their way around a sportster engine.

I think you should go for it :)

Cheers
 
Exmoor beast said:
Evel Knievels motorcycle deal ship in Bute. Even the pickup truck is cool. Ironically, imported motorcycles and not a Harley to be seen. His Dad owned a bike shop and gave little Bob a BSA bantam to learn the ropes on.
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Nice G80CS in the window! El Camino is also my favourite ute, would have one immediately if they weren't such guzzlers. Instead of a LS swap, maybe a TDI implant? ;)

piet
 
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