My Project and a few questions

Rohan · Jun 28, 2013

Matt Spencer said:
The Early Widelines , the sub frame top ( & bottom ? ) Bolts went right across , so fed through
the tube welded across in the Oil Tank . Had a Rubber Tube thrown in that . Fairly Satisfactory .

Where you getting this from Matt ?

Early (road) featherbeds the oil tank sat on a plate across the top of the gearbox plates, 2 bolts to hold it there.
Rubber mounted with as much rubber as squeezes into there - and dissolved by any stray oil.
No connection to/with any frame bolts...

Rohan · Jun 28, 2013

Bevelheadmhr said:
The intended use? As a road bike, with as much power as I can squeeze out of the engine while keeping it reliable. Standard Ironhead XL1000 make about 55bhp at the rear wheel and weigh 525 lbs wet.. aiming for 75 bhp plus and at least a hundred pounds off the standards weight.

Sportster forums quote that iron motors stock rear wheel horspower is more like 45, if you are lucky ?
Since thats about what a stock Commando gives, and the Commando was faster ??
55 is more like "brochure" horsepower - at the crank - on a good day ?!
Horsepower costs $$$ - how fast do you want to $$spend$$... !

Looking good...

acotrel · Jun 29, 2013

That is a very lovable motorcycle. 55 BHP is almost enough to have fun with, especially if a 5 speed CR gearbox is fitted. I don't know what the XR750 Production Racer turned out, however I suspect it wouldn't been a whole lot more. I doubt that my Seeley 850 turns out over 60 BHP, however the torque is immense, and you can use the close gears to climb up in top speed. You won't know how good or otherwise your bike is until you try it. You might find that it will pull very high overall gearing. As Rohan says horsepower costs dollars. In going down that path there is usually a trade-off between low end torque and top end power, and the mechanical problems are part of the journey. If you want to drag or race the bike, you might be better to use methanol fuel with a good dose of nitro, and leave the rest relatively unchanged.

Bevelheadmhr · Jun 29, 2013

The specs for a std 79 Ironhead are 61 bhp at 6200rpm and 52 lb/ft torque at 3200. These numbers are as 'claimed' by HD. I believe these are at the crank. Knock off approx. 12 to 15% for rear wheel figures, and you get low 50's bhp. In std trim, an XL1000 was tested by cycle world with a max speed of 113mph, and did the quarter mile in 14.22sec (13.3sec with the muffler removed).

I expect the motor to be making around 60bhp at the rear wheel, with the big carb, electronic ignition and less restrictive exhaust. To gain another ten or so, It'll be getting PB+ cams (these will make a big difference), lightweight pushrods, mildly cleaned up heads and maybe a touch more compression. I wont be dragracing it, though I may take it to Pendine Sands next year. As for drag racing, we're building this...

URL=http://s1122.photobucket.com/user/Merch131ho/media/Compbike/ironhead42004.jpg.html]

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Rohan · Jun 29, 2013

Bevelheadmhr said:
The specs for a std 79 Ironhead are 61 bhp at 6200rpm and 52 lb/ft torque at 3200. These numbers are as 'claimed' by HD. I believe these are at the crank. Knock off approx. 12 to 15% for rear wheel figures, and you get low 50's bhp. In std trim, an XL1000 was tested by cycle world with a max speed of 113mph, and did the quarter mile in 14.22sec (13.3sec with the muffler removed).

Over on the Sportster forums, they are saying about 45 or 46 hp at the back wheel.
Nortons also claimed 60 brochure hp, but only dynoed about 45 at the rear wheel.
Those numbers are a bit slower than the early 70s Commando too.
If it truly had 55hp at the back wheel, it should be faster and quicker than that.
Even with the mufflers removed its still not there....

Torque is strong low down, and falls away as the revs go up, doesn't it.
Be interesting to see the torque curve, that would have to breathe well to make that hp at such low revs (relatively).
What we need is someone who has put one on the dyno.
Where is that Cycle test when you need it..

Bevelheadmhr · Jun 29, 2013

Yes, I've seen those numbers too, but even they comment that a free flowing air filter and pipes give an extra 7bhp at the rear wheel, which brings us up to 52bhp, that's with the stock carb and no engine work. The cams its getting will let it make power to 7000rpm. I have access to a rolling road dyno, so when its complete, the bike's fueling will be set up on the dyno, and I'll find out what it really makes.

lcrken · Jun 29, 2013

acotrel said:
That is a very lovable motorcycle. 55 BHP is almost enough to have fun with, especially if a 5 speed CR gearbox is fitted. I don't know what the XR750 Production Racer turned out, however I suspect it wouldn't been a whole lot more. I doubt that my Seeley 850 turns out over 60 BHP, however the torque is immense, and you can use the close gears to climb up in top speed. You won't know how good or otherwise your bike is until you try it. You might find that it will pull very high overall gearing. As Rohan says horsepower costs dollars. In going down that path there is usually a trade-off between low end torque and top end power, and the mechanical problems are part of the journey. If you want to drag or race the bike, you might be better to use methanol fuel with a good dose of nitro, and leave the rest relatively unchanged.

Not sure what a production XR750 makes, but the modified ones do pretty well. I watched Mert Lawill's XR750 crank out 90 rear wheel hp on Axtell's dyno over two decades ago, and I'm sure they've improved them since.

Ken

Rohan · Jun 29, 2013

lcrken said:
Not sure what a production XR750 makes, but the modified ones do pretty well. I watched Mert Lawill's XR750 crank out 90 rear wheel hp on Axtell's dyno over two decades ago, and I'm sure they've improved them since.

The XR was a rather different beast to the road irons, of course.
Having 2 separate inlet manifolds, and carbs, makes for a much better inlet tract system.
And also gives both exhaust ports facing forward, not unimportant for better cooling.
They also went to alloy heads long time before the road bikes got them ?

We've had this discussion here before, but Buells got a somewhat strong motor there, in various forms ?

Bevelheadmhr · Nov 10, 2013

A quick update, as I've almost finished making the exhaust system, using reverse cone megas and stainless headers. Still need to polish them. I wanted them a little higher and more tilted upwards, but that's as high as they can go and clear the gear change linkage. I may move the rearsets forward in the future (they are a long way back) which would allow me to cut and re weld the downpipes and raise the megas a little.

Jeandr · Nov 11, 2013

Good looking bike 8)

Jean

cjandme · Nov 25, 2013

It is looking good indeed, keep the updates coming,

Bevelheadmhr · Jan 27, 2014

Almost ready to be taken apart to get the frame powder coated and all the alloy parts polished. Wasn't happy with the exhaust so remade it.. hope to have on the road by April..

chilly · Jan 30, 2014

Nice project , Lance Weil would have approved 8)

Wouldn't mind a leccy start on my 72 CH these days

Bevelheadmhr · Apr 13, 2015

I finished the bike last year, not had much chance to ride it since, due to injuring my arm, so looking forward to this summer to get some miles under its wheels. On the road weight is 415lbs with 2 gallons of petrol. Not had it on a dyno yet so don't know the rear wheel hp.

Bevelheadmhr · Apr 13, 2015

P.S. I put together a step by step build thread on youtube. with more photos and details than I posted here. Its my first attempt at such a thing, so be kind. The background music runs out after a couple of minutes and I have no idea how to make it continue...

https://youtu.be/dn-VGHidxzs

Jeandr · Apr 14, 2015

Good looking bike

Jean

Fast Eddie · Apr 14, 2015

That's a crackin' lookin' bike you've built there matey.

All credit to yer!

worntorn · Apr 14, 2015

Nice! 8)

Glen

dave M · Apr 14, 2015

It's very nice to see this bike come to fruition, you have done a beautiful job. I will be building a similar machine with an ironhead motor in a Slimline Atlas frame, I was just in the US and drove from Carmel to L.A. And back (about 11 hours) to collect the engine (1975) and frame (1972) that I bought on Craigslist two years ago.

Where have you put the battery on this bike? I imagine it must be fairly beefy to oprate an electric start. I was thinking of converting mine back to kickstart to save a few pounds.

What did you finally do to the engine and are you satisfied with the power output? I was intending to put in some slightly hotter cams, decent carb and electronic ignition. Like yourself mine will be for a bit of fun on the street, more a poor-mans Norvin than anything else - as you point out the parts are cheap and readily available.

I enjoyed your Video, thanks for being so generous with your information.

Bevelheadmhr · Apr 19, 2015

The battery lives under the seat, its Lithium and very small with plenty of power to turn over the engine. It weighs only 1kg compared to over 6kg for the equivalent 20ah Yuasa. The engine is pretty stock, bar the carb and electronic ignition. Undecided as yet if I'll fit different cams or higher CR pistons. I have other bike projects to be getting on with now. It goes very well, handling reminds me of my old SS900 desmo.. very stable but still light on its feet. Gearbox has a big gap between 2nd and 3rd,but its just something to get used to. The rear shocks are a little soft compared to the forks, so a shock upgrade is on the cards when funds allow.

My Project and a few questions

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