I'm about to split the crank case on my 1974 247 montesa would anyone know what seals and size are needed and should I replace anything else while its apart..

While you've got the cases apart it would make sense to replace the main bearings. These and the seals are available from Inmotion, www.inmotiontrials.com.

 

Good luck with removing the gear pinion from the crankshaft!

Thanks cleanorbust... I was only afterr the sizes as john lee motorcycles is 200 yards away from home and Charlie said get me the sizes and by us a pint an ill sort them for you lol ... I've just ordered the main bearing thanks again. Pinion a problem then?

This is is my engine seals list in spanish. Hope you'll find it easy to translate with Google.

 

Eje primario del cambio semicárter izquierdo (lado embrague) 1 x medidas 20/30/7 
Eje tambor selector semicárter izquierdo (lado embrague) 1 x medidas 22/32/7 
Eje secundario del cambio semicárter derecho (lado encendido) 1 x medidas 17/28/7 
Eje puesta en marcha semicárter derecho (lado encendido) 1 x medidas 17/28/7 
Eje del selector semicárter derecho (lado encendido) 1 x medidas 15/24/7 
Ejes del Cigüeñal (lados izquierdo y derecho) 2 x medidas 25/35/7, 20/30/7 en cigüeñales de cuello fino ó 25/40/7 en la Impala 2 
Tornillos cierre semicárteres 12 x juntas tóricas diámetro 7,0 mm interior x 1,5 mm grosor 
Eje palanca embrague (tapa izquierda motor) 1 x medidas 14/20/6 

Ruedas 
Retenes bujes ruedas 4 x medidas 23/40/10

Take care when you split the cases as the gears run on individual needle rollers. There are three sets, three in each, and each set are a different length but same diameter. If the gears and shafts spill out when you split the cases you'll have fun working out which needle rollers belong to which gear because it's not obvious and they will each fit on any shaft but the gears won't slide if they are in the wrong one.  I think one of the manuals - clymer? - may give the correct lengths, but better to keep the box intact in the ignition half case when you split them.

 

Also, the crankcase screws have O rings on them as they don't screw into blind holes like most but go straight through with a nut on the end. You may have to source new ones if they are too crushed to re-use (just in case you think someone may have fitted them for an odd reason and throw them away as they don't belong)

 

Also watch out for shims on gear shafts and there are shims either side of the main bearings so note where they are fitted and how many either side.

 

Get the big end properly checked as well as no point putting it back in if it's showing any wear - you only want to split a Montesa engine once...

 

Remember all the threads are 7mm so don't lose any countersunk screws..

 

Crank sprocket is on a taper, so a bitch to remove - as can be the final drive sprocket, also tapered

Unfortunately trying to remove the gear from the crankshaft can turn into the kind of challenge that leaves a competent mechanic in need of therapy, a mere quivering shell of his former self. All manner of heating, pulling and battering has been known to be used to crack the problem of the gear tightening itself onto the shaft over a 40 year period. On the other hand you may be lucky...

Sorry, meant to say that the numbering on the seals I bought is as follows:

D058 1

TC 25 40 10 TTO

Hope this helps.

Sorry for the late thanks but top info Thanks all