First ride with NEW head

Well guys, I've finally got my MK1 850 back with it's new Fullauto Technologies head and I rode it first yesterday and then for a few hours today. Apart from some muck in the carb (34mm Mikuni) which gave me the half throttle blahs, it was great. I had to fiddle with a few carb adjustments to cure some off idle fluffiness and then it was just fantastic. A noticable boost from 2000rpm up and pulled really well to 4500 revs. That's as far as I've gone due to the fact that it's running +60 pistons with a rebore so I have to bed the rings in. It's hard to describe but it feels like a 750 instead of an 850 if you get my drift. Somewhat easier revving than an 850 (the bottom end was left alone with the standard cam). Definitely stronger than it was in the midrange and mine ran very well as it was. I'll be back on it every day now so I shall add stuff as I go for your info. I'll even give it a bath and a polish and a love and post some photos.

Hi, nice to hear ! you've done a pretty good job, any more info about D shape inlet?

FullAuto,

What is the difference between yours and stock? Not looking for trade secrets or anything, just in general. Although I had heard some rumblings about XR750 style inlet tract, I was under the impression that it was the stock configuration.

Checked with CNW about them the other day and they said that there were shipping issues with the heads but expected them later.

Put on your salesman hat and give us your pitch.

Z

I'm not much of a salesman Z, but I'll give it a go. The heads are standard configuration except for the material and heat treating (6061-T6) and the port configuration. Jim Comstock designed the ports and at this early stage I can say, definitively, that they work with a strong midrange. The valve seats on both 750 and 850 heads are suitable for unleaded (of course). Unfortunately, due to poor packaging, the three heads sent to CNW were damaged in transit and have been returned to Harrop Engineering for scrapping. We now have custom boxes in which the heads are individually packed so this will not be an issue for the rest of the batch.
If you look at the ports, the exhaust ports are much smaller than standard with a flat bottomed "D" shape. The inlets have a shape I would describe as "Cobra's head" shaped. All very nice. Unfortunately, Harrops were going to do me a batch of ten which would have covered the immediate orders, but have now decided to finish the batch of fifty in one hit. Therefore, they are still a few weeks away. Then, I will have enough to go around and I promise not to run out of stock forever.
Hope this answers your query, now, I'm off to ride my Norton.

Cheers, Ken.

Cost? even in the orders-of-magnitude range? (with valves, guides, springs, etc. i.e., bolt-on shape)?

Matt at CNW is selling them at around US$1800 odd dollars. This is for a head with guides and seats fitted. Bolt on your Norton stuff and off you go.

Thanks Ken. I'm saving my pennies...!

Thanks, FullAuto,

That's just the information I was looking for.

Regards,

Z

Are there any differences except for material when compared to Comstocks mods on a stock head? Port size, runner length etc? Tony

Good question Tony. As far as I'm aware, the port shapes are what he uses when he ports a head and adds material. The exhaust ports particularly are small by comparison with standard heads but I'm out every day now piling on the miles and the difference in grunt is obvious. I purposely left the rest of the motor stock except for the rebore so that I had at least a seat of the pants comparison. Wish I'd been able to dyno the thing beforehand, but it just didn't work out that way at the time. Stock cams, Boyer and a 34mm Mikuni. My other motor is now a 920 with a PW3 cam just waiting for a new head to arrive !! That one should hoot. It's got a pair of 36mm Dell'ortos at the moment and I'm not sure which way to jump yet, carburation wise. I've got a bit of time up my sleeve there so I'll decide later.

Here she is.

I like that color :wink:

BillT said:

I like that color :wink:

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Me too!

I once had a 1969 Commando "S" I painted with a very similar color. I like brightly painted Commandos. The black one's appear too sedate for my taste. My current Combat is a 1995 Mustang red metallic. DuPont Chroma base at $75 a pint.

It's not an 850 colour as far as I know. It is the original colour on this 750 tank and fibreglass side panels. I'd presumed it was Solid Signal Orange and it wasn't until recently that I saw a post saying that the 750 SS and the High Rider colour was tangerine. They look the same in photos to me but I suppose I'd never paid that much attention. Also, from what I've seen, the 750s in the Solid Signal Orange had Gold striping and detail, whereas the High Riders I've seen have the silver. I'm not necessarily correct, this is just my observations.
Do I care that my colour is not original?
Not one bit.

I've done about 400 miles now and everything is bedding down nicely. This thing now grunts from nothing and is pulling like a train. I'm going to start revving it out through the gears shortly to see how the top end goes, but the mid range is just fantastic.

Thank you Jim Comstock.

Well, more than a week on the bike now and 500 miles covered. I really cannot believe how strong the motor feels. From 2000 rpm it just hauls, short shift, open the throttle again and it keeps coming. I've hit 6000 rpm now and there's no top end rush, just an even power spread. The improvement is dramatic. Even more so when you consider that I run a 23 tooth gearbox sprocket so at 50mph she's only doing 2500rpm. I just wish I had a few demo bikes out there.

Fullauto said:

Well, more than a week on the bike now and 500 miles covered. I really cannot believe how strong the motor feels. From 2000 rpm it just hauls, short shift, open the throttle again and it keeps coming. I've hit 6000 rpm now and there's no top end rush, just an even power spread. The improvement is dramatic. Even more so when you consider that I run a 23 tooth gearbox sprocket so at 50mph she's only doing 2500rpm. I just wish I had a few demo bikes out there.

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If you need to seed a few heads for "review" I'm sure there are one or two volunteers on the forum willing to help. :mrgreen:

Here I am!!!!!! LOL LOL :lol:

haha I know right.... If I had a job I'd prob buy one

I'm planning on it I just need to let the wife get over the shock from the last build.