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Tx 240 engine


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It's wonderful to join you all

I have a tx 240 but the disc valve came loose and jammed,

I would say it's a catastrophic engine failure as the flywheel slipped, crank gears slipped, disc valve broke in 2. Flywheel previously welded on and crank taper is in bad shape.

Cylinder and piston are fine and bearings all ok

Where would I start looking to get a rotax 240 engine to replace my old one or part to fix her.

I bought a rotax 122 engine but it would require some fabrication to work- drive sprocket won't fit its too low for the chain. We're worried about the strength of the frame if we start cutting.

What alternative engines are there for this job. Preferably 2t but if 4t is easier and fresher and has been done before. It's not for competing just a project but due to the age of her we want to do it right

This bike is the same as a swm gori and Armstrong 

The sprockets are on the right if your sitting on the bike

I am open to your ideas and any help would be much appreciated

Many thanks


Edited by Kdtx240
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1 hour ago, teamferret said:

i've heard of the climber bottom end being used

Easy to do, problem is electronic ignition is now getting old on climbers. Better with a point ignition which can be swapped for a new electronic if required. 

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Thank You all for your replies

Thankfully the points in ignition system is working

The magneto is a bit tired but it still makes power

Hopefully should be able to get parts to build her up

Will post updates for you all , may be take some pictures so we can all enjoy the upcoming build

The tx 240 has been a challenge but a very enjoyable one. 



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  • 6 months later...

Hello everyone

It has been a while since I posted 

During this time I have been sourcing a new engine

The bike was almost burned in a fire but it escaped untouched and is securely locked away now

A tx312 engine has been sourced and will be fitted in due course

Will post updates as they happen

Thanks all



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  • 5 months later...

Hello all

The engine has arrived and is in my possession. Due to the way things are at the moment I can’t get to the frame to get the engine in. However patience will win and I’m not putting my dearest friends at risk over a bike.

Allen’s used trials spares got the engine for me for which I am very grateful.

Here is the engine 



I am also building at a 1992 kx125 9279B692-AE50-4F91-9530-99BF6819FD99.thumb.jpeg.99c78a835f7776328e64c8d0924bb2ef.jpeg1D735633-1F5F-4205-AF56-8BF6A06A50DC.thumb.jpeg.233397abac785dff3349493ff1cbafad.jpeg

and a 1990 CR250 


Hopefully these photos and the much awaited news of an engine for the tx will lift your spirits in these challenging times.

If you would like more information about my bikes please ask



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Just an update on the kx 125

Engine is in 

Has spark after full rebuild

Need a radiator hose so go to parts store on Monday

Build the rest of her and try start

Kawasaki seems to have aged better than the Honda but the Honda is a simpler machine

May try and get the tx 240 frame and keep up the good momentum


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Update on kx 125

Near all built.. have managed to lose the front sprocket 

getting close to the first start.. I’m a bit nervous because I’ve a lot tied up in this little 125

After the kx is complete it can come off the stand and the tx240 can begin 

it all began with the tx240 and a can do attitude and asking questions 

there is a ty80 for sale in my area for 900 is that a good deal?

Here are some bonus photos 












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Update on tx240

frame is home

will take a day to remember a bit about the bike.. looks a very simple bike 

few bits to tidy up 2 quite awkward jobs to do. One drilling out a engine mount bolt on frame. other is wiring 

frame is in my shed ready for building 



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Update on tx240

Engine is in

I need to rotate the intake boot to the outside by a bit less than 180 degrees as the motor is actually off a Swm hoping if i loosen the clutch cover it will just move a bit.

Front engine mounts may need to be adjusted but it's held by one stud so it's going nowhere

New points on the motor and every bearing has been done in the bottom end. This motor also makes a lot of compression. 

Plan is

to get the engine fully mounted by either making new front mount brackets or play around with the ones there

Trace the pickup or signal from the points and get spark

fire her up

Make a chain slider

Put chain back on

Go test ride

Tidy up front forks do seals

Tidy up few wee bits

Then enjoy the tx240

I may not repaint her only cover bare metal but leave her vintage

Tldr engine in.  bit of adjustment needed but very minor work.

Party on




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Good evening all

Tonight I spent some mechanic time with my tx

I was able to take off the clutch cover and move the intake boot so that the carb would go on. All that holds it on is a hose clamp. One of the dowels is actually a bolt hole too.

I got the engine mounted apart from the broken stud. It will need an m6 nut welded on, heated up and slackened that way. It took some prying with a prybar to get it lined up. It was either the heat of the fire or just the Italian way. Here I called on my experience of fitting gearboxes to cars along with my experience of bikes. 

I think the next step is to get spark and start her up 

I feel the broken stud can wait to such times suited to delicate work

I really do feel we are getting very close to the first start

I do notice this is a very large cylinder, I think it's a 311 engine it's definitely the largest displacement bike i own now. If anybody knows what the actual cc is please advise. 

I can't praise enough how good of a job has been done with the engine i think the crank has even been rebuilt it is basically a brand new engine. 

Will keep you all informed



Edited by Kdtx240
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Hello again

Got the carb on and figured out the wiring. 

We now have a nice strong spark

seems to take very little speed of kick to make a spark. 

Have hit a problem with the exhaust not fitting.. Shouldn’t be too big of an issue.

we’ve got spark, the carb works so we’ve fuel and we’ve compression.

will keep you all informed of new work.

regards kdtx240


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  • 4 weeks later...

Hey everyone 

so the last 2 Saturdays have been spent on the tx 240

got the exhaust on

had to timesert a rung head stud this was not fun at all

made a chain slider

i need an air filter may fit a k&n to the carb and not need any air box 

and the decompression valve had to be removed to fit the old tx 240 exhaust to the swm 280 head 

the bike creates a lot of interest now due to its age and “footery” work






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