Topic: Reaching 70hp with a 500/4

[HondaFreak]

Please see a photo of the extended cooling fins on the 500/4 cylinder block.

[slikwilli420]

Please see a photo of the extended cooling fins on the 500/4 cylinder block.

That is awesome! Really looks like the Japauto cylinders made for the 750 engine back in the day. Ill bet that took forever but cooling is king on a vintage racer.

[HondaFreak]

I understand that it took an age to add material, by welding, and then fettle it back to a fin.
I have screen shot the engine off my phone. It shows the basics of the breather system. There is a catch tank that fits where the starter motor was. You can see that there is a vent on the dry clutch cover and another from the cylinder head cover. They both breath into the starter motor tank, which then breathes into a second tank that you can see mounted to the frame. This in turn breathes to atmosphere. You can see that the breather tubes are quite large diameter.

I hope this is useful.

[slikwilli420]

I understand that it took an age to add material, by welding, and then fettle it back to a fin.
I have screen shot the engine off my phone. It shows the basics of the breather system. There is a catch tank that fits where the starter motor was. You can see that there is a vent on the dry clutch cover and another from the cylinder head cover. They both breath into the starter motor tank, which then breathes into a second tank that you can see mounted to the frame. This in turn breathes to atmosphere. You can see that the breather tubes are quite large diameter.

I hope this is useful.

Interesting. Why the second tank? I would think just venting to atmosphere out the top of the one in the starter area would be plenty. Thank you for the picture.

[HondaFreak]

I think there were initially some issues with the motor breathing heavily, which have been resolved, but it also has to run 4 x 37¾ mile laps in the IoM at the Classic TT, so it is best to be safe. The bike spends a lot of the lap 'flat out' on the TT course.

[simon#42]

the minimum size of catch tank is 500cc for the engine and 250cc for the gearbox , this could be the reason for two

[livefast_dieold]

I think the choice is just Dunlop or Avon. I will check though. What sizes are you using?

Conti's come in 2 sizes per tire: front 110/80 or 100/90, rear 150/65 or 130/80.
I've tried them both, currently using 110 front and 150 rear. The narrower set was good as well, I switch to the larger ones as they give me more confidence in the corners, also bike is lower by a couple of cm which is not bad (also my bike is probably 30kg heavier than a 500/4).

I would never go back to Avon! I was wondering how we can possibly use them a few years ago! I guess we were riding differently to adapt to those tires.
Also, I see how the comment from the riders: "it scrubbed off too much speed on the fast corners" can hold true with Avon tires... they move around a lot actually, and the bigger the tire the more it flobbes around.

Last weekend there was the first race of the italian championship (got 3rd :-) ), someone had the new Pirelli Phantom! They look really nice with the vintage treads, can't say anything about grip yet, as both bikes that had them didn't finish the race

[slikwilli420]

I think the choice is just Dunlop or Avon. I will check though. What sizes are you using?

Conti's come in 2 sizes per tire: front 110/80 or 100/90, rear 150/65 or 130/80.
I've tried them both, currently using 110 front and 150 rear. The narrower set was good as well, I switch to the larger ones as they give me more confidence in the corners, also bike is lower by a couple of cm which is not bad (also my bike is probably 30kg heavier than a 500/4).

I would never go back to Avon! I was wondering how we can possibly use them a few years ago! I guess we were riding differently to adapt to those tires.
Also, I see how the comment from the riders: "it scrubbed off too much speed on the fast corners" can hold true with Avon tires... they move around a lot actually, and the bigger the tire the more it flobbes around.

Last weekend there was the first race of the italian championship (got 3rd :-) ), someone had the new Pirelli Phantom! They look really nice with the vintage treads, can't say anything about grip yet, as both bikes that had them didn't finish the race

Interesting to hear people moving away from Avon so quickly. Lots of championships won on those tires. If the Conti had a better reputation in the rain I would probably switch. I'll get this season out of my Avon's then be ready for some new shoes. I would say the majority of AHRMA has moved to the Conti.

I looked up the Pirelli Phantom and they are listed as a road tire so I would never think to use them racing, MAYBE a track day, but not really the right tool for the job to go racing.

[livefast_dieold]

I think the choice is just Dunlop or Avon. I will check though. What sizes are you using?

Conti's come in 2 sizes per tire: front 110/80 or 100/90, rear 150/65 or 130/80.
I've tried them both, currently using 110 front and 150 rear. The narrower set was good as well, I switch to the larger ones as they give me more confidence in the corners, also bike is lower by a couple of cm which is not bad (also my bike is probably 30kg heavier than a 500/4).

I would never go back to Avon! I was wondering how we can possibly use them a few years ago! I guess we were riding differently to adapt to those tires.
Also, I see how the comment from the riders: "it scrubbed off too much speed on the fast corners" can hold true with Avon tires... they move around a lot actually, and the bigger the tire the more it flobbes around.

Last weekend there was the first race of the italian championship (got 3rd :-) ), someone had the new Pirelli Phantom! They look really nice with the vintage treads, can't say anything about grip yet, as both bikes that had them didn't finish the race

Interesting to hear people moving away from Avon so quickly. Lots of championships won on those tires. If the Conti had a better reputation in the rain I would probably switch. I'll get this season out of my Avon's then be ready for some new shoes. I would say the majority of AHRMA has moved to the Conti.

I looked up the Pirelli Phantom and they are listed as a road tire so I would never think to use them racing, MAYBE a track day, but not really the right tool for the job to go racing.

Conti aren't bad in the rain. People here used to switch to Heidenau/ Avon during rainy sessions, but then came the classic random guy that went for a pole position under heavy rain on Conti because he hadn't "rain" tires and prove everyone wrong. So no one is changing tires here anymore, is Conti with whichever weather. Check the continental page: it seems that the new CR3 are coming out!

As for the phantom, they are not available for sale yet, so you are looking to the regular street tires.

[slikwilli420]

[/quote]

Conti aren't bad in the rain. People here used to switch to Heidenau/ Avon during rainy sessions, but then came the classic random guy that went for a pole position under heavy rain on Conti because he hadn't "rain" tires and prove everyone wrong. So no one is changing tires here anymore, is Conti with whichever weather. Check the continental page: it seems that the new CR3 are coming out!

As for the phantom, they are not available for sale yet, so you are looking to the regular street tires.
[/quote]

I saw a new 3CR coming out and have inquired when they will be in the states. My Avons will work for now, but the 3CR is on my list once available.

[HondaFreak]

This is the latest 500/4 piston made to match the new head. All going together over the weekend for dyno runs next week ahead of the Pre-TT.

[MRieck]

This is the latest 500/4 piston made to match the new head. All going together over the weekend for dyno runs next week ahead of the Pre-TT.

Looks like a Chevy intake valve could fit in there

[HondaFreak]

Now there's an idea. You guys in the US are the 2V specialists. I have often looked at the chamber design.on some of the racing V8's. There are some very nice aluminium rollers rockers to be found too :-)

[Sam Green Racing]

Now there's an idea. You guys in the US are the 2V specialists. I have often looked at the chamber design.on some of the racing V8's. There are some very nice aluminium rollers rockers to be found too :-)

Peter, I think Yoshi made roller rockers back in the 60s for the CB72/77 250 and 305 twins, it might be worth John digging around to see if there is anything like them still around.

Sam.

[HondaFreak]

Oh did they? I haven't seen those. I will have a dig around on the net & see what's around, information wise. Thanks Sam.

[HondaFreak]

Found them, Sam - as attached. Also Takegawa are making them for pit bikes, which are mostly old tech Honda style 2V engines, as I understand it. Does anyone make roller rockers for the 750?

[Sam Green Racing]

The Takegawa ones look nice Peter.
Good luck finding something for the 500.
I've no idea who might make them for the 750.

Sam.

[slikwilli420]

I used these guys to have my 750 arms hard welded:

http://www.rockerarms.com/pages/contact.html

They did a bang up job and rocker arms is all they do. They were also substantially cheaper than every other place that offers hard weld rockers. Might be worth a call.

[HondaFreak]

Two 500/4 bikes & two 350/2 Davies Motorsport bikes ready earlier today at the Pre-TT in the Isle of Man, ahead of practice tonight.

Alan Oversby was the quickest 500 by 3 seconds (lap time) and Dominic Herbertson an impressive 4th on his first outing on the 500 on the Billown Circuit.

I will endeavour to keep the results up to date for those interested.

[Sam Green Racing]

Good luck Peter and Team Davies Motorsport.

Sam.

[RAFster122s]

Good luck with the practices and races, prayers for safe racing.
David

[andyman]

By the way, what happens with the 350/4 Davies racebike. Was there not enough Power? I think in 2013 Classic TT William Dunlop rides a Davies 350/4....

[MRieck]

Two 500/4 bikes & two 350/2 Davies Motorsport bikes ready earlier today at the Pre-TT in the Isle of Man, ahead of practice tonight.

Alan Oversby was the quickest 500 by 3 seconds (lap time) and Dominic Herbertson an impressive 4th on his first outing on the 500 on the Billown Circuit.

I will endeavour to keep the results up to date for those interested.

Nice stable of bikes right there.

[HondaFreak]

Firstly, the 350/4. It was raced in 2013 but it was sold on, as someone wanted it for parading. It had potential but the 350 twin is such a good engine/bike that I think, in the end, it wasn't worth the amount of work it'd have taken to make the 350/4 competitive.
Unlike the 500/4 which gave 64-65bhp reliably from the outset; some 5bhp than the unreliable 500 twin.

The DMS riders were 1-2 in todays 500cc class practice. I will post the timing sheets later.

[andyman]

@HondaFreak: Thanks for answer. Yes the 350 Twins are good engines.

By the way, how much power had the 350/4 2013?