Hello fellow Montesa owners!

[gtowndualsport]

Hello everyone,

I recently purchased a 1973 Montesa Cota 247 to use in vintage trials. I live just outside of Memphis, Tennessee, USA in Germantown. This bike is replacing my TY250.

I have ordered a fair amount of parts from InMotion Trials. They are great to work with. I have a few questions regarding the bike. I have an owners manual. The information in it is sparse to say the least. I've read extensively on the forums. If anyone knows the answers to the following questions, I would appreciate your advice.

1. What is the stock chain size? I believe it is a 428. Just not sure.

2. I'm using synthetic premix. I've been running 40:1. It seems to run fine with little smoke. Anyone had problems running this lean with synthetic premix?

3. Will GL-5 gear oil hurt the transmission? I've read that you should use only GL-4.

4. What about the clutch? Will synthetic motorcycle 10W30 make it slip?

5. What weight fork oil do you use in the forks? I have several bottles of fresh fork oil.

6. Is there anything that I should look out for in maintenance? Any known issues with these bikes?

7. Any recommendations on parts suppliers? The suppliers in the USA seem to demand a high premium for parts. This is partly due to the small number of trials enthusiasts compared to Europe.

Thanks so much for your opinions. Hopefully, I won't reinvent the wheel here. So far, I love this bike. I just want to keep it running for the next 50 years.

John

 

[kingscorpion]

1. The correct size is 520.

2. Even at 50:1 every synthetic oil will be enough.

3. GL-4 is better, but GL-5 probably is an acceptable choice. It will hurt the "yellow metals", but at a high temperature.

4. Mineral 10W30 or 10W40 is a better choice. 

5. SAE 20 is the original oil.

6. Their maintenance is very simple. Just take a look at the points and condenser, and keep the carb clean.

7. Jared Bates at Southwest Montesa is a nice guy. We miss a lot John Haberbosch; he passed away a few years ago and had a deep knowledge of these bikes.

You've made a good choice. It's the right bike to ride for 50 years. Just two advices:

1.- Use Dunlop tyres. Specially the rear wheel has a narrow rim, and the rigid Dunlop flanks will make a difference with the modern Michelin.

2.- Try to find a 9 teeth front sprocket. You can't figure the difference with the 10th until you test it. The modern renthals are easy to find.

[cleanorbust]

Looks like you found a decent original one. Secondhand parts come up on eBay pretty regularly.

Would be worth checking the ignition timing - should be 4mm btdc for this bike. 

There was a good handbook for all Montesa offroaders published by Clymer in the USA in the 70s, you may well be able to find one. It'll guide you through a full strip down if you ever need it. Good advice re the 9t sprocket: Inmotion do them but you could be in for some fun removing the original - it's a taper fit. A Pitman puller works best, along with lots of determination if it's been there for the last 40-odd years.

I'd check under the fork gaiters for rust on the stanchions. If they've been left covered for years there could be a horror story beneath.

Your biggest problem could be the fibreglass tank, which modern petrol will destroy. Lots of discussion available on the net on using sealants to protect the inner surface of the tank, but I'm glad my '79 model has the separate alloy tank under fibreglass cover.

PS: make sure the kick start lever isn't fitted too far forward, if it is the shaft can punch a hole in the casing. If you post a pic of the other side of the bike we can advise if it's OK at the moment.

Edited September 8, 2017 by cleanorbust

[gtowndualsport]

kingscorpion,

Thanks for the informative response.

1. The correct size is 520.

I asked about the chain size because I tried to put on a new 520 chain last night. It wouldn't fit through the chain tensioner. I have a new chain tensioner on order through InMotion.

2. Even at 50:1 every synthetic oil will be enough.

I think that I'll stick with the 40:1 ratio unless I start having problems with fouling.

3. GL-4 is better, but GL-5 probably is an acceptable choice. It will hurt the "yellow metals", but at a high temperature.

I just found a bottle of SAE 90W GL-4 at NAPA Auto Parts during lunch. It is marketed for marine engines, but it should do the trick. 

4. Mineral 10W30 or 10W40 is a better choice. 

On the way back from NAPA, I stopped by Honda and got a bottle of dino juice 10W30.

5. SAE 20 is the original oil.

I'm thinking that I will go with Belray 10W fork oil.

6. Their maintenance is very simple. Just take a look at the points and condenser, and keep the carb clean.

Got it. Thanks. Will do.

7. Jared Bates at Southwest Montesa is a nice guy. We miss a lot John Haberbosch; he passed away a few years ago and had a deep knowledge of these bikes.

I'll check out Southwest. I've heard a lot of good things about them. I also found a site that I hadn't seen before. (clasicaslegendarias.com) They have a huge Montesa section.  Has anyone had any experience with them?

 

I just put a new set of IRC trials tires on. I really liked them on my Yamaha. I know what you mean about the Dunlops. The original Dunlops were on the bike. They were falling in pieces, but I still had a nightmare getting them off. I finally gave up with spoons and visited a friend's shop with a tire changing machine.

I will take your (and cleanorbust) suggestion and go with a 9 tooth front sprocket. I'm going to order a 9/48 combo.

I have attached a picture of the gear oil container.

 

[gtowndualsport]

cleanorbust,

Thanks for the info. I have already ordered a Clymer's manual. I try to only use non-ethanol gas. I have attached a picture or the right side of the bike.

Do you guys use regular unleaded or super to mix? We have 87, 89, and 91 octane here. I think that 87 octane is equivalent to European 91MON. The gas station with non-ethanol gas only has 91 octane. I should be good using that.

[cleanorbust]

Yes, your 90w for the gearbox should be OK (300cc). I use ATF in the clutch case (200cc).

Ethanol-free fuel is the ideal answer but it's rare and expensive here in the UK. 91 octane should be fine. I use regular unleaded, 50:1.

I think I run my kick start lever one spline back (anticlockwise) from where yours is.

Looks like the standard chain tensioner, so the 520 chain shouldn't be a problem.

The original footrests are a bit pathetic, being too small and smooth. I got a pair of modern style Raceline footrests from Motomerlin in England, which fit the U- shaped bracket on the frame with a little grinding of the rests so they sit at the correct angle. Most modern footrests are unsuitable because of course they fit the single bracket design of modern bikes.

Looks as though your bike doesn't have the second plug hole to the right hand side of the head, which is handy for fitting a decompressor, a useful addition for some sections and a foolproof way of stopping an over-revving motor. Cylinder heads with the second threaded hole are regularly available on eBay.

Enjoy the bike!

 

 

 

 

Edited September 8, 2017 by cleanorbust

[jc2]

Very good advice about the position of the kickstarter. I can't remember now whether it's the 1 o'clock or 2 o'clock position for the kickstarter they say not to exceed.

From memory its at the bottom of the stroke where the stop tab punctures the case if you have it too far forward.

 

Nice bike by they way.