New SWM 350 Jumbo owner - a few questions...

[drca]

I am the new proud owner of a 1983 SMW 350 Jumbo, in all it's yellow glory.  Bought it from a local rider (thanks Wayne!).  The engine has been fully rebuilt and has just a couple of hours of riding on it.

I guess over the next few weeks (month?) as I get familiar with the bike and start riding it / tuning it to my liking I will have many questions.  This Trials Central has been a great source of help in the past so I am turning to you guys again for answers.

Engine oil

What engine oil do people use?  I my (modern) trials bike I use Maxima MTL 80WT.

How to verify oil level and refill? There are no oil level windows (unlike my Fantic) and I couldn't find an oil refill cap.  So I assume it's one of the screw on the clutch case.  Is that right?

Premix ratio

What is the recommendation for premix ratio when using modern pre-mix oils?  I have so many gas cans (from 32:1 to 130:1!) for various bikes / two strokes engines in my garage that I am hoping one will fall close enough!

Stock jetting

What's the stock jetting

Carb rebuild kit

Carb is leaking...  I did a thorough cleaning, needs a rebuild.  What's the recommended place to get genuine Dell Orto parts?

Suspensions

I am on the heavy side so I'll need stiffer springs (it just bottoms riding on the trails!).  What's the recommended rear shocks and where to find stiffer springs in the front?

Many more questions coming, so thank you all in advance for your help.

DC

[kurtas]

Very neat looking Hydraulic clutch conversion.

I have a TL320.

Gear Oil - I use ATF fluid but can't see a problem with what you have suggested, and yes you remove the SHCS behind the gear lever to set the level.
Key thing to do is to remove the drain plug (using a Hex Drive) and not the kickstart stop bolt (which has a Hex Head) when draining the oil.

Premix - every answer is valid depending on how you want to ride the bike, I normally ride at 80:1 in competition trials but if you are doing trail work I would look at 50:1 with the modern synthetic oils.

Suspension - If you just bottom on trails then you are probably set up perfect for a competition trials event.

MotoSWM in the UK are most helpful for parts and information.

[htrdoug]

Never had bottoming troubles with the black Ozo shocks from InMotion, get the 50lb springs(just tell them your weight) cheap, quick shipping to USA.

BTW, Hydraulic clutches aren’t usually permitted in Vintage Trials events, Jumbo clutch isn’t too bad with a fresh set of cables, look to see if the lever is still on top of the cylinder head that reduces pull strength required.

[dozerash]

 What brand is the hydraulic clutch? 
I have a TL320, run 60:1 Amsoil Dominator, 80wt Bel Ray Gearsaver (Maxima is good too), I use OZO shocks with heavy springs. 

[dozerash]

I take the plastic plugs out of the clutch cover and tip the bike in a pan to drain oil. Works well for me. 

[pschrauber]

Hi,

that is a very nice SWM you have there and the most powerful twinshock trials bike produced.

 I have previous build smaller model NW.TL 320 from 1980, which I like very much.

To the mixture I use 1:67 or 5l of gasoline to 75ml of synthetic or half synthetic oil with a low burning point together with Ultimate gasoline with ingredients for cleaning up build up carbon, also providing extra octane as at least my SWM tends to ping when it is hot (over 25 degrees celsius).

To the engine oil I use Elf HTX 740, because I use in any bikes I own and it improves the clutch action in general a bit most automatic oils work well too.

To the Dell'Orto carburator there are carb rebuild kits to each model available which provide all gaskets and seals you need, but I would recommend to look up slide needle needle nozzle and the jets too if they are not showing wear or got damaged by wrong cleaning maintenance.

For the right jetting you should provide the carb model and size mounted.

The rear suspension looks not to be original and the spring with its many windings looks too to be on the soft side, you might look up Rockshocks from Gary Fleckney.

To the front springs I don't have an solution may be Wirth in Germany or Bultaco UK / InMotion?

[dozerash]

 I use HFS suspension for the fork springs. They are really nice! Just make sure you give them all the information on your forks and old springs. 
https://suspensionhfs.com/en/

 

[fourex]

This is info from the 1980's, pretty sure MJ was 100.

Carb Jetting.pdf

Engine Oil.pdf

[Tr1AL]

On 3/11/2024 at 11:57 PM, kurtas said:

Very neat looking Hydraulic clutch conversion.

I have a TL320.

Gear Oil - I use ATF fluid but can't see a problem with what you have suggested, and yes you remove the SHCS behind the gear lever to set the level.
Key thing to do is to remove the drain plug (using a Hex Drive) and not the kickstart stop bolt (which has a Hex Head) when draining the oil.

Premix - every answer is valid depending on how you want to ride the bike, I normally ride at 80:1 in competition trials but if you are doing trail work I would look at 50:1 with the modern synthetic oils.

Suspension - If you just bottom on trails then you are probably set up perfect for a competition trials event.

MotoSWM in the UK are most helpful for parts and information.

is that a mistake 80:1 mix in a motor that is air cooled ?

[lemur]

1 hour ago, Tr1AL said:

is that a mistake 80:1 mix in a motor that is air cooled ?

From MC-1 product data sheet:

• Equally suitable for air-cooled or liquid-cooled high performance motorcycle 2T engines

• Also suitable for all types of 2T engines including lawn mowers, weed eaters, trimmers, chainsaws, leaf blowers, snow blowers and more

Manufacturers are pretty careful with making unsupported claims that could kill their business and experience tells me it will work just fine if the oil has 80:1 or even 100:1 printed right on the packaging.