Need help showa forks bottom out k-tech

If the forks have been worked on by K-tech, I think there could be 3 options as to what they did, a revalve, a 20mm cartrige kit or a 25mm cartridge kit. The last two are less likely as they are £400 upwards and are in reality track only. The forks will be sprung to a given rider weight and they provide a data sheet showing spring rate, oil type and grade, air gap and suggested settings.

The likelihood is that you'll need fresh oil as a minimum and new springs depending on the weight they were built for.

If you know the name of whoever had the work carried out you might be able to get the necessary info from K-tech to do this work independently. If you don't, by far the best solution is to send them back to K-tech, they will know what's been done when they look inside and they can sort them out to your requirements (probably cost £120-£150, but check that).

I've had 5 sets of race bike forks modified and the 2 sets that K-tech did were better than anybody else's efforts (inc Maxton). It's a bit of a shame you are so far from Leicester where K-tech are based, although they may well have a reliable Scottish agent.

The cheap, but risky option is to add 20mm of fairly heavy oil to each fork and wind up the compression damping a bit to see what happens.

As said your forks probably need more oil. The damping curve in the last third is greatly affected by the air gap in the forks. (you can compress springs and air but not fluid). if the previous owner was a light rider he would have needed less oil otherwise his weight transfer would never overcome the rising rate of the fork compression to get proper travel. if your heavier you are breezing through the travel before the compression rate ramps up enough to stop you. Setting the sag will tell you if the spring rate is wrong. if you can't get less than about 40mm of sag with you on in gear without loads and loads of preload then the spring is too soft. My money would be on the oil though.

I'd email K-tech and ask their advice first

Mad Biff, this bike sounds familiar, what year is it mate?

EDIT: Ignore what I said mate, Ive just seen the pics in ya profile

I'd email K-tech and ask their advice first

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This is a good plan, they will probably have made a set up for something like Motul 5 weight oil, so it will be bloody rubbish if you fill it with Silkoline 10 weight.

Also the Showa forks get very fussy once the air gap drops much below 100mm. The only K-tech data sheet I can find for similar forlks is for my RS250 proddy racer (very similar forks), but K-tech use a 100mm air gap in those, so that's probably a starting point.