9 replies to this topic

[DAVEY_C]

i think their the same as the k1100 but anyone got 1 they wouldn't mind parting with??
cheers

[Sam Walters]

Argh........Don`t drill it by hand. Do it on a mill. 76mm side to side 86 front to back.

The front three at a reference

[DAVEY_C]

hi sam, thanks for your concern but i wasn't going to... a bloke i use to work for has an industrial size pilar drill, well not quite a mill but i assumed it'd do the same job, and he said he'd do it for me
are them measurements bolt centres, where is the starting reference point or are you starting from the 3 holes that don't require plugging??
thanks pal

[Sam Walters]

Yes exactly that. if this is the route you're taking. As soon as its been drilled I.E. one hole. Run the tap in a little bit with the pillar drill just turning it by hand. This will ensure the head studs aren't tapped wonky!

I presume you're being a sensible boy and going dry deck?

[DAVEY_C]

aha i get ye, so i'll have a guide thread to run the tap through the rest of the way
yes i'll drydeck it, wouldn't have it any other way , as far as i know i have to anyways because its going on a bored 998.

block will be bored to suit k100`pistons by a suitable machine shop and then decked once i figure out if there's a more suitable crank to bring them closer to deck height. i have the complete head, injection/fuel systems, looms and pistons to get started with.

[Sam Walters]

Word of advice, go for mini pistons imported from Australia. Deck flush to them.

You cant regrind a 998 crank as you wont get rods to fit unless you want to go custom.

You may as well go for slightly higher rpm rather then slightly more capacity when using the 1098 crank. You're looking at a net power of around 95-105hp without any head work and the non rs cams.

Think of it like this. the 1098 crank can only really take 6000rpm of abuse. the 998 can take 8000 if properly modified and balanced.

The difference between 6000 and 8000 rpm is 33%. The difference in extra capacity the 1098 has over the 998 of 10% seems pointless when you look at it like that.

Edited by Sam Walters, 08 December 2011 - 05:46 PM.

[DAVEY_C]

thanks sam, your advice is valued.
with aprox +120 would the capacity not be aprox 1215? the problem is i'm on quite a tight budget compared to what it realy should cost so i'm doing it over a time instead of cramping it together.
i did consider the ozzy pistons origonaly but found it hard to fit them into the budget and when these pistons came up as a bargain i sorta took them as a possibility. i was reading on here alright about the difference in rev range but thought it would be acceptable to consider the 1098 crank in a road mini and see what other modifications can be done to the head to make it a bit more torquy because i should probably have it refurbished anyway, i was thinking of swapping the k100 trottle bodies for the k1100 items.
thats basicaly what was in the pipeline but for the moment i'm still gathering parts... i do see your point about the pointlessness and if its not worth i'll have to change.
would it be possible to achieve a more torque engine instead of a high reving engine this way or are the bike cams more suitable to high revs?

[Sam Walters]

With a quick number crunch in my head. its about 1040cc with the +120. That extra 175cc capacity really isn't worth it.

The engine will be more stressed for any given rpm. Plus you're seriously limiting your head room!

The k100 head on a mini block will pull from massivly low down. I would not worry in the slightest about tractability!

Even the 300 degree cammed 1380`s from JohnK are kittens below 5000 rpm then give that kick!

Firstly you've got to source a crank. You would have to have the pistons machined for the pin and you may even have to have the rods machined.

You may not find it cheaper to just buy the 120 pistons.

[DAVEY_C]

thanks sam, i might just reconsider my spec to suit your recomendations, it is true in what you are saying that between finding a crank, reeming the rods to suit pins and excessive milling from block surface would possibly amount to more than getting suitable mini pistons and having them valve recessed... i thought this conversion would result in nice increase in pull ability but nothing like your suggestion... put a on my face!!

i can go ahead so and start having the block plugged and new stud holes done to get started.
would you have an idea of a c/r i should be aiming for?

[Sam Walters]

thanks sam, i might just reconsider my spec to suit your recomendations, it is true in what you are saying that between finding a crank, reeming the rods to suit pins and excessive milling from block surface would possibly amount to more than getting suitable mini pistons and having them valve recessed... i thought this conversion would result in nice increase in pull ability but nothing like your suggestion... put a on my face!!

i can go ahead so and start having the block plugged and new stud holes done to get started.
would you have an idea of a c/r i should be aiming for?

Static compression ratio should be dependent on what cams you wish to use.

So pick your power output and choose your weapons.