31K(TM)

[urbantangleweed]

Early days, but this looks like it might just work......

[JonW]

ahh love this. I was building a Ktmaha a while back but shelved the idea, it was the opposite of what youre doing, tho i might have another go in a year or so when my projects run out.

[urbantangleweed]

I couldn't decide on KTMaha or YaKaTaM, but also settled on KTMaha! Trickiest bit is going to be the exhaust, gearchange might need a cunning solution too, but other that rather, it's looking reasonably straightforward.

[urbantangleweed]

Looks like that lines up pretty well to me 👍🏻

[JonW]

that does line up well!

In case you fancied a read, this was mine: www.2smoked.com/KTMaha_-_Half_KTM_250EXC_Half_RZ350_Supermoto.html

[urbantangleweed]

It's a shame that never got completed just due to bureaucracy. Not a problem here as long as the bike the engine goes into is already registered, pretty much just build it, change the details with the DVLA and ride it. In fact, you can build just about anything you want but it then might have to go through a motorcycle single vehicle approval test but it's not too bad.

[JonW]

Yeah, sucked but at least I used some of the parts. I still have the frame parts and a spare ypvs engine, so who knows

Excited to see how your idea comes off. Not sure what engine size yours is, but my old 250EXC made 50bhp so if youve a 300 or 380 you should be laughing.

[urbantangleweed]

It's a 250, but it should still be quite sprightly! The engine is far lighter than a YPVS so power to weight ratio will possibly be better.

[Deleted]

i like the 31K(TM) moniker

really clever, interesting build

Have fun

[urbantangleweed]

Just fitted a pair of TT600 calipers, designation has now changed to the KTMahumph RD250EXC-TT

[oldbritguy]

This looks interesting

Are you going to see how many different manufacturers you can incorporate into the build and expand on the KTMahumph RD250EXC-TT?

Might end up getting ridiculous on here   with some of our imaginative members

John

[urbantangleweed]

I don't have enough tank space for a longer name Jon, I did this afternoon trial fit a VF400 radiator I had kicking about, technically that would make it a KTMahumphda RD250EXC-TTVF, probably too little side panel space for that!

The calipers do look good though and bolted straight on. Ignore the mackled up bolts, they're all I'd got but shiny new ones are on the way.

[Deleted]

31KTM250TRDVF the challenge is on

Mind you he'll probably start fitting suzuki bits to it next and we're all fooked

[urbantangleweed]

Nov 13, 2019 20:25:57 GMT 1 @hblair said:

31KTM250TRDVF the challenge is on

Mind you he'll probably start fitting suzuki bits to it next and we're all fooked

Ha! I did look at a pair of RGV250 calipers I've got but the TT600 ones bolt straight on and the calipers, hoses, master cylinder and lever came to me for £80 so it was a no brainer really.

I have been toying with KTyaMahumph.....

[JonW]

Im loving this project

[jh002]

Is this engine counter balanced? Just wondering what vibration like I’m not familiar with Ktm

[urbantangleweed]

Nov 13, 2019 22:58:33 GMT 1 jh002 said:

Is this engine counter balanced? Just wondering what vibration like I’m not familiar with Ktm

As far as I'm aware there is no counterbalance shaft in this engine, they are also rigidly fixed into the frame, No fancy rubber mounting. I raced a 200 in enduro for several years and vibration was never a problem, but that was in a solid and stiff KTM chassis, not a wobbly Japanese chassis that's now 34 years old. It is something I've contemplated, but I think the way to go is get it built and see what it's like. I'm only really building this because I want to, it might be an unmitigated disaster or, it could be the wildest thing I've ever ridden (not likely, a Honda CR500 has held that crown for nearly 30 years!). Basically, I'm building it because I can and I'm very interested to see what it is when it's done. I'm just having a bit of fun really!

[JonW]

Yes these are a buzzy motor, its just that off road you dont really notice it as youre too busy avoiding the flora and fauna. On the road my 250EXC seemed acceptable for short rides. Wet road, new off road tyres, light weight and light switch power meant your sphincter muscles could get a workout tho. lol. I will say that this motor in a road frame with a bit more weight and road tyres it will be fun I reckon, tho it wont be the frightening powerhouse one of these can be when off road and you accidentally grab a handful of throttle lol. I do think it will be more than fine for town and twisties as its a revvy beast with adjustable powervalve etc I always wanted to fit motard wheels to my KTM but it was a bit too noisy for the commute (and I had a 620SC SM for road use at the time). Doing the conversion this way means you might well have more room to use a quieter pipe and that would help, tho it would take away the great noise these make.

If you consider that a DT125 makes 12bhp (17ish derestricted?) and a DT200R makes 38ish. Those bikes weigh a bit less than the 31K, but this motor makes 48-50 or so bhp so it wont be a slouch. The 250 YPVS made 47-48bhp according to Yam, IRL it would have been less. This has less weight as well as its got less engine/exhaust weight etc. I'll be very interested to hear what you think when its done.

Re the vibes, you could mount the motor to the frame using some rubber bushes, and weighted bars will help.


>I'm just having a bit of fun really!

This is what this type of project is all about I reckon! Thats why i love this and enjoyed the time I spent on my KTMaha even if it was a dead (it may only actually be dormant?) project ultimately. Lots of projects are the same on here as most people (me included) build a variation on an RD/RZ using Yam parts, it takes a lot more imagination and a bunch more problem solving to do something like this. I also like the fact youre doing this without a massive budget, the same way I did mine, ie the use what you got or can get easily and make it fit.

Actually if you look at this sub forum you can see there are more 'different' projects on here now than ever. Triples, 4 bangers, different frames etc etc. I think as a group we are now starting to think outside the normal RD/RZ box and the forum is all the better for it. Guys are engineering great rides and the forum members get to learn or teach them along the way and the project is all the better for it.

[urbantangleweed]

Nov 13, 2019 23:54:08 GMT 1 JonW said:

Lots of projects are the same on here as most people (me included) build a variation on an RD/RZ using Yam parts, it takes a lot more imagination and a bunch more problem solving to do something like this. I also like the fact youre doing this without a massive budget, the same way I did mine, ie the use what you got or can get easily and make it fit.

I've got a completely standard F2 (apart from TSA pipes), an RD/RGV hybrid and a standard-ish 3HM1, the 31k chassis was sitting here waiting to become a 31K again, I have the correct engine ready to go in but I decided I didn't want another RD variant, 3 was enough (some think it's more than enough!). The KTM was bought a couple of years ago simply because it came to me at a good price, I'm too old and knackered to do anything serious off-road these days and so the KTMaha project was conceived! I'm really enjoying finding solutions to the issues involved with marrying two things together that were never meant to be and hopefully by next Spring, I'll have something fairly unique, it might end up being an unusable pile of sh1t that rides terribly, but by the same token, it might end up being a tremendously fun thing to ride. Time will tell......

[urbantangleweed]

Fabricated a small extension piece to mount the coil and roughed out the rear engine mount brackets, need to get some spacers made up before I can finalise them.

[dusty350]

This looks great - very different !
Now, I wonder if my brother in law still has that CR500 lurking in his shed ??

Dusty

[urbantangleweed]

Spacers arrive so set to and finalised the rear engine mount brackets, all slotted together quite easily and engine is firm. Existing front mount picked up nicely on the original YPVS engine mount so that was nice. Laser Monkey confirmed chain alignment is pretty good. Now I'm happy with the engine position, I can measure and order up some spacers for the front mount, now just need to come up with a cunning plan for the bottom engine mount.

[Deleted]

That is coming along real good

Great news on the mounts

[urbantangleweed]

Levers all mount up well, carb fitted, need to see if I can adapt and fit the original airbox or at least some of it, new YSS shock replaced the old knackered one and then the wiring to sort. Found a rad which should do the job, it's also got a fan switch so will look at rigging one of them up too. All in all, not going too badly so far. Biggest headache once again is not being able to weld, will have to draft someone in who can hopefully come and weld the bottom engine mount to the frame, is there anyone in the Loughborough area who can weld and works for tea and biscuits? Then I need to get an exhaust made......

[JonW]

wow! 'leaps n bounds'! Such fast work puts us all to shame

[midlifecrisisrd]

Mot'd by the weekend then 🤣

Steve

[urbantangleweed]

Nov 21, 2019 17:08:16 GMT 1 midlifecrisisrd said:

Mot'd by the weekend then 🤣

Steve

Yeah, don't know which weekend that'll be though! 🙂

[urbantangleweed]

With a bit of jiggery pokery, the KTM air filter fits in..... just!

[urbantangleweed]

The KTMahumph took a couple of leaps up the ugly tree today, really not sure about it, but I like the nod towards its off road roots.....

[urbantangleweed]