Hi, i have just bought a Montesa Cota 348 1978 bike. Does anybody know the correct 2 stroke mix and any advice on synthetic or regular? I was told 25% but that seems high.

This might be a daft question, it has a twin plug head, one central and one offset. Why? Am i ment to swop the ht lead over depending on what kind of riding i am doing?

Thanks for any advice.

Jim

The centre top plug hole is for the spark plug and the other is for a decompresser valve which can be useful for going down drops

http://www.trialscentral.com/forums/index....showtopic=18424

Edited August 8, 200818 yr by fellonmelug

Yes 25% oil is too much.

It should run fine if you use somewhere between 33:1 (3%) and 50:1 (2%), full synthetic or semi-synthetic.

Ideally you should not use two different oils together so either continue to use what is in it already or drain the fuel tank and carby first if using a different oil.

Jim - There is a very useful site at www.todotrial.com/.../manuales/manualcota348.htm which has some downloadable info on your bike. mostly in Spanish I'm afraid.

I use castrol tts fully synthetic @ 50:1 ratio on my Bultaco's. Most Spanish twinshocks of this era run a similar mix.

If you are searching for info on your bike use google image finder and use Spanish terms (like manuales) as well as english. I found this the best search method.

There is a wobblers series at berkhamsted MCC Nash Mills site (which is also a practice site I think) http://www.berkotrials.com/home.htm. I found that wobblers trials are a bit thin on the ground near to Oxford (where I am based). I found it best to enter pre65 events which usually cater for twinshocks also and ride around and have a go at the easier sections. Cheltenahm hawks (whittington) and Mortimer Classics (Reading) are nearby. Both clubs are very friendly and helpful. Volunteering to observe is a great way to get to know everyone and watch technique and VERY welcome by the clubs. North Berks as a great and friendly Club but they have among their members some very good riders and even their club events reflect this. I found getting a twinshock around the easy sections very difficult and daunting especially at Seymours Arena which has very unforgiving lumps of concrete (as my row of broken gear levers will testify).

Tim

Thanks for the replies. The todotrial site is excellant, even though i can't read a word of Spanish, a great help. Thanks Tim.

I went to the wobblies trial at Nash Mills last week and joined the club the same day. Just waiting for my riding gear to arrive and i will be out practicing.

This might seem a obvious question, but i am not used to 2 stroke mixing. A 50 to 1 mix, how much would that be in cc/fl oz to the gallon?

Thanks

Jim

Thanks for the replies. The todotrial site is excellant, even though i can't read a word of Spanish, a great help. Thanks Tim.

I went to the wobblies trial at Nash Mills last week and joined the club the same day. Just waiting for my riding gear to arrive and i will be out practicing.

This might seem a obvious question, but i am not used to 2 stroke mixing. A 50 to 1 mix, how much would that be in cc/fl oz to the gallon?

Thanks

Jim

Based upon the number of questions I see on Trials Central, regarding how much oil goes in a gallon, or liter, of gas for a certian ratio, I am assuming that you guys must not have these in the UK?

This is a Ratio-Rite mixing cup. There are ratio scales on the side, and you just pour oil in, up to the line, that matches the ratio you want to use. The scales are in columns, depending on the amount of fuel you are mixing the contents into.

Super simple, and takes all the guesswork out. For what it is worth, 50:1 is still probably more than you need. Fully synthetic at 60:1 is extremely common here. All in my group (247, 348, 349, TY250's, etc.) run 60:1, except for one club member who runs AMSOIL at 100:1 in his Bultaco Sherpa T. He has for several years now, with no problems at all. I am just not that brave!

50:1 equals 2 oz per gallon, get a ratio cup, they are easy to use, should be able to get one at most any bike shop

I do not use 50:1, I'm a bit closer to 32:1, 4 oz per gallon, it's my motor and I can run what I want, I believe the popular choice for trials bikes is 80:1, I like lubrication in excess, it works for me

Over here it's more common to use cc and litres rather than oz.

For 50-1 mix use 100cc of oil to 5 litres of petrol.

(i.e. for every 50 parts of fuel use 1 part of oil)

Briefly here's how to work it out.

1 litre = 1000cc.

1000cc divided by 50 (the mix ratio) = 20cc

20cc x 5 (litres of petrol) = 100cc

A nice range of graduated mixing jugs are available from the Missus kitchen!!

Jim, I don't live far from you (Kettering) and am trying to get my Montesa sorted. Don't be shy and introduce yourself if you see me at any Trials.

Edited August 8, 200818 yr by steve

Montesas should be 3 or 4% oil mix, i e 25/1. maybe 30/1 minimum.

S_M.

Edited August 8, 200818 yr by 348mate

Hi, Thanks everyone for the excellant response, now i understand the ratio system. Just treated myself to a small jug from asda to measure the oil.

Thanks again

Jim

Montesas should be 3 or 4% oil mix, i e 25/1. maybe 30/1 minimum.

S_M.

They were back in the day, when we wern't using synthetic oils. With fully synthetic, it is a different ballgame.

They were back in the day, when we wern't using synthetic oils. With fully synthetic, it is a different ballgame.

Can someone explain to me why this should be so ???

S_M.

Synthetic oil has a higher film strength than mineral oil at the same temperature so it can generally be used at a lower ratio for the same protection.

Synthetic oil creates less visible smoke if used at the same ratio.

Using synthetic oil means it will take longer to clog up the exhaust pipe with gunk and form carbon deposits in the exhaust port and inside the head and on the piston crown.

An air cooled motor sees a very wide operating temperature range which puts it more at risk of lubrication film failure than a liquid cooled motor.

Synthetic two-stroke oil resists film failure due to high temperature better than a mineral oil will.

It's not all good though. A fully synthetic oil is not as good at protecting the engine internals (conrod bearings in particular) from corrosion when it is not being ridden. My bikes sometimes don't get a run for months at a time so to provide good corrosion protection I use a semi-synthetic two-stroke oil.

I live in a very hot climate and sometimes have problems with motors overheating during the extremes of use (my Cota 348 in particular is prone to heat related problems) so tend to mix my fuel for air cooled two-strokes on the conservative side at 3%. If I lived somewhere cool where motors have an easier life, I would probably use a lower ratio like 2% in my air cooled motors.

A fully synthetic oil is not as good at protecting the engine internals (conrod bearings in particular) from corrosion when it is not being ridden.

Why do you say that?