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 Post subject: K100 on 1220
PostPosted: Wed Jan 03, 2018 3:13 pm 
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848cc
848cc

Joined: Wed Jan 03, 2018 3:02 pm
Posts: 3
Hi guys,
I’ve recently been searching here in Nz for a k1100 head and a cheap 1275 that would suit a rebuild, I’m not having much luck. I’ve decided to look at other options and have found a k100 8v head for sale and should be able to pick up an 1100 for a couple of hundred dollars.
Just wondering if anybody has done this yet and if so were they happy with the results? It’s a lot of work and money but if i could get 100hp out of it I’d be pretty happy.

Any thoughts?

Thanks


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 Post subject: Re: K100 on 1220
PostPosted: Thu Jan 11, 2018 11:57 am 
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Bimmer Twinky
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Joined: Mon Sep 06, 2004 4:36 pm
Posts: 8594
Location: Brisbane
fitting the K-series cyl head (whether its 8v or 16v) to a small-bore (998 or 1098) is a lot more troublesome than fitting to a 1275, i would recomend doing it to a 1275
yes i`ve done many K-series cyl head conversions & still have plenty to do
not many people have done it to a small-bore, but thats because its more of a pain for less pleasure

nothing wrong with any K head, however the K1200RS version is the best, they have thinner valve stems than the K1100 & the later k12 has larger throttle bodies

the K1100 (16v) head is also excellent
the K1000 (8v) LT model is the lowest flowing of the lot, so fitting to the smallest motor is not such a great thing, altho it is still far better than the average small-bore 5-port motor, problem is that it`s a whole lotta work , time & money for not alot of gain

so,,, if it were me, i would try to find a 1275 to fit any of the K-heads ontop of
if you do (however) choose to go the 8v onto a small bore then i suggest you move the whole head over to the front (alt/dist) side of the block, repositioning "all" the holes to suit, as there is an issue with head-stud/bolts interfering with both the water jackets & the side-plate area,,, & its a pain to repair.
cheers & have fun, & we have plenty of k-series heads & 1275 blocks here, just be a bit dear sending them across the creek to you
Matt 0407 135 656

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.


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 Post subject: Re: K100 on 1220
PostPosted: Thu Jan 11, 2018 9:27 pm 
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998cc
998cc

Joined: Fri Aug 30, 2013 8:59 pm
Posts: 862
Location: Western Sydney
Not wishing to hijack this, but what HP can you expect from the 16V head on a 1275 ?

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 Post subject: Re: K100 on 1220
PostPosted: Tue Jan 16, 2018 2:21 pm 
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848cc
848cc

Joined: Wed Jan 03, 2018 3:02 pm
Posts: 3
Hi Matt

Thanks for the reply, I have found just bought a k100 head with throttle boddies and all for a pretty good price here, I may have also found a 1300 Austin engine, which I assume just need a mini box attached to the bottom of it.
I’m trying to do this on the cheap So thought of the small bore route as a possible option.

In the meantime I’m going to take the head into work and start the modifications.

Can anything be gained from getting the head ported? And is it best to approach motorbike guys for this?


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 Post subject: Re: K100 on 1220
PostPosted: Tue Jan 16, 2018 5:28 pm 
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1275cc
1275cc
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Joined: Thu May 24, 2007 7:19 pm
Posts: 5307
Location: Yandina,Sunshine Coast,QLD
Matt knows best but I'll have a go. Yes it will flow better if ported and their is a bit of meat that can be taken out (I don't know where), most head shops should be able to do it but if you can find a bike place with experience with them then your laughing.
The Austin 1300 should be the correct block but if its RWD the crank will be wrong.

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 Post subject: Re: K100 on 1220
PostPosted: Wed Jan 17, 2018 7:57 pm 
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Bimmer Twinky
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Joined: Mon Sep 06, 2004 4:36 pm
Posts: 8594
Location: Brisbane
yes "all" the K-series heads have a little lip inside the ports where the machining meets the cast port,,, with valves out you will feel it with your finger,,, round it off, blend it in, so the lip is gone & that`s all you "need" to do,,, removing any-more meat or trying to open the ports more will most probably take you backwards a step,,, unless you plan make the valve-seat holes huge & fit huge valves (which really isnt necessary)
they flow very well with just that little mod , as the ports are already a tad big & if you look closely one side of each port is "biased" so there`s a little pocket in one side,,, quite a large area really,,, filling the bottom of the port helps but it`s way way way too much to go into here as things can get quite critical, you would want a flow-bench & some play-time filling & removing & shaping & well,,, we`ve been there & it`s painfull,,, but there are gains to be made "after" you have played a LONG time on the flow-bench

as ive said, they`re already very good heads,,, just tidy up those lips inside the port-bend & you`ll be sweet
cheers
Matt

_________________
No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.


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 Post subject: Re: K100 on 1220
PostPosted: Sun Jan 21, 2018 3:18 pm 
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848cc
848cc

Joined: Wed Jan 03, 2018 3:02 pm
Posts: 3
Thanks for the replies guys.

Matt, I think i should be paying you for this information haha. Not many people would go out of their way to offer that sort of information and advice. I bought the specialist components build guide, but feel like it's more of a sales brochure. I think I've learned more from your posts than anything in that book.

I ordered a copy of David vizards book online about porting and flow testing on the weekend so when I get it I'll have a read through and see if building a flow bench is something I want to pursue. I might find it a bit too much of a learning curve and seeing as I will also be building an engine for the first time, however it is a project about learning new skills and not about final numbers on a chart.

Thanks again

Ben


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