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.
After many years of driving, I also had a problem with the engine shutting down, after approx. 10 to 20 minute ride on my 2009 GG280 TXT. I Couldn't restart engine while warm. There was no spark on the spark plug. When I replace it, the engine runs for about the same time, then it shuts down on its own. I replace the ignition coil with a spare one, the spark plug still has no spark. Then I happen to find your wiring diagram and check the resistances on the ICM connector and notice the problem that the resistance on the BLK/RED wires is 0 Ohm instead of 20.9 Ohm. Both other resistances were very close to the prescribed ones.
Member drca, I thank you for providing this schematic because it allowed me to get a quick diagnosis.
I usually play with the clutch pack thickness until I get the feel I want at the lever and engagement speed that works for me. Best way to adjust clutch pack thickness is to swap steel plates with different thickness. you can get them from Splat Shop: https://www.splatshop.co.uk/dp-gasgas-pro-clutch-steel-plates.html
Their page even shows the recommended thickness range for each model year.
M20 bolt works fine. You can use a nut / washer and a piece of tubing to use it the same way a flywheel puller works. This way no need to bang / pull etc... Works like a charm.
Getting back stuff together is another story tho... You can't bang the 1/2 axels back in as the edges are not tapered. What I did was to really carefully visually align everything then gently pushed in the 1/2 axles. Take a little bit of doing and about 3 hands 😁
From talking to my dealer, there is a small brass screw on the left side of the bike that should be the primary way to adjust idle on the bike. Range of adjustment is less than on regular carburetor but sufficient for me.
Adjusting the throttle stop (as indicated above) should "theoratically" require to reset the TPS from what I understand.
Short version: Does anyone know if TRS can be registered with the DMV in California?
Longer version: For those not living in California, bikes need to be registered with the DMV to legally ride on public land. This does not mean that they will be street legal, but they will get a Off Road Registration and appropriate Off Road sticker. DMV will NOT register bikes from manufacturers that have not been "approved" (or at least registered) with the California Air Resource Board (aka CARB). So... I am looking at buying a TRS and I haven't heard whether these bikes are registrable with the DMV in California.
My experience is... install new clutch within or close to specs, try... if you don't like it, adjust thickness, repeat.
Measure the pack with a good caliper, wet (not dry) and with a reasonable squeeze on the caliper. If you have new fiber plate, let them soak in oil overnight (some fiber plates use to swell a bit, especially in tranny oil if you listen to the old man tales!). Make sure you also measure each steel plate in multiple place around the circumference to make sure they are even and then make sure the plates are flat (use a piece of glass and you should not be able to see light between the glass and the plate). It doesn't hurt to check the fiber plates too.
Thicker clutch pack will make for a faster clutch engagement, but less progressive and a harder pull and possibly more drag (beware that Gas Gas TXT Pro clutches have a reputation for drag anyways). This is the setup for advanced riders, good for zaps, etc...
Thinner clutch pack will make for slower clutch engagement, but more progressive and lighter pull and possibly less drag. This is the setup for "not so advance riders".
When reassembling the case on the bike, make sure the put a dab of grease on the thrust bearing and washer on the slave clutch cylinder to keep them in place during assembly. They can slip during assembly and drop in the engine (don't ask me how I learned that... the only thing I would say is that it was an expensive lesson).
In my experience (YMMV) oil viscosity also has an impact on clutch drag, but not much on engagement speed (I use Maxima 75W). I never tried tranny oil, I know as many people who love it as people who hate it. I've learned to live (and embrace) the clutch drag.
Clutch pull: it seems that going to Silicon based Brake Fluid (DOT 5) makes the pull a little lighter (it's less viscous than the mineral oil and is compatible with the mineral oil clutch master and slave cylinder). But in the end, a good Hand Grip Strengthener device is your best friend against stiff clutch pull 😁
Short story: I am looking for feedback on what's the general experience in getting Gas Gas parts and service under the new KTM ownership
Longer story: I have a 2013 Gas Gas TXT which I have religiously maintained and upgraded throughout the years: Tech + Ohlins suspensions, Braktec brakes, did a full rebuild of the engine - new top end, changed every single bearing and seal in the engine, etc...). I do love my Gas Gas and I could maintain it and rider it for many years to come but I have the new bike hitch (I am in California and there are new emission regulations coming down that makes it the right time to get a bike).
I know that KTM has done a lot of things to promote the Gas Gas brand (mostly MX and enduro bikes tho), but the fact that they require every dealer to have trials bikes on the show floor is a great thing I think.
I would love to get a new TXT, but... having been a Husqvarna owner during the BMW to KTM transition (and a Husaberg owner during the transition too), I can tell you that this was a nightmare: new dealers didn't want support the prior year models, older dealer didn't have access to parts, KTM didn't buy the inventory of parts for the prior year models, etc... etc...
I am hearing that the Gas Gas to KTM transition is following the same model: I know for sure that my local dealer(s) don't know sh*t about trials bike, and I am not even sure that I would trust them doing any work on a non-KTM or Husky bike (I am hearing from former Gas Gas dealer that are getting new Gas Gas owner asking them to work on their bikes!).
I have also heard that getting parts for the newer bikes is a challenge. I had switched to buying parts from the UK a long time ago (better service, better availability, better expertise, better prices, faster and cheaper delivery) but the small Gas Gas dealers in the UK have been squeezed out too... So that might dry out too.
So any feedback, success or horror stories on how's life for Gas Gas trials bike owners under the KTM control would be great.
I am looking for recommendation for a place to send my crank to get it rebuilt (I have new rod kit). Someone with experience (and any necessary jigs) with Gas Gas trials crankset would be great.
That's an impressively compact clutch they've built for it!
The clutch was designed by XIU-rdi. These guys (Josep Serra “Xiu” is the main guy I believe) have some pretty impressive credentials in the trials world, including designing the TXT Pro, the Ossa TR 280i etc.
I recently purchased a 2020 Gas Gas TXT 250. I have about 15 hours on the bike. I have the freeplay adjusted properly at the perch and am running the recommended 75w/90 gear oil, which was changed after about 2 hours.
With my clutch lever fully engaged to the bars, the bike wants to creep forward. If I put it on a stand the rear wheel turns when in gear and the clutch lever engaged to the bars.
Is this normal? I am new to trials and to this bike. I find that it actually helps me when balancing etc., but don't want to smoke my clutch.
I did a search before I posted, and I couldn't seem to find anything to answer my question.
Thanks in advance for any help!
I have a 2013 Gas Gas TXT Pro 250 and my experience is that there is always a little bit of clutch drag on the bike (and I believe that I am not the only one). It's worse when the bike is cold (cold oil). Too much drag can be not only annoying but possibly dangerous as it can cause the bike to stall at inopportune times.
Oil wise, some people recommended ATF (never tried, or the Elf brand (very hard to find in the US). I use Maxima MTL Transmission Fluid 75wt ($10 at my local Cycle Gear) and I've been pretty happy with it.
It's unlikely that you will "burn" your clutch on a trials bike short of riding stupid!
Adjustment wise, you might want to try the shortly levers like the Apico's Flex levers. They allow to adjust independently the reach and engagement point. That might help too.
The Gas Gas clutch is actually pretty good and better than most traditional spring designs. The diaphragm clutch is used by GasGas, Ossa, JTG, TRS, Vertigo, Sherco-Scorpa and Electric Motion.
The thing to know about the Gas Gas clutch is that it's highly (and easily) tunable by adjusting the clutch pack thickness (3 fiber plates + 2 steel plates):
Thinner pack makes for an easier pull and a slower engagement (which is what most riders at the beginner to intermediate level will need). If you go too thin, you'll get clutch slip tho.
Thicker pack = harder pull at the level and much faster engagement.
By fine tuning the thickness of the clutch pack you can go from a bike that will be mellow and easy to ride to a bike that will want to jump up 4' ledges when you dump the clutch. At my level (SI), and age (!), I go on the "easy" to ride side. But I have experimented with various configuration and this is definitively something you can feel at any level.
How thick or thin should you go? Below are Gas Gas recommendations. Honestly I don't understand why the numbers change depending on the year, but they should be a good place to start. And in my experience, these are really guidelines and considered as starting points for your own experimentation.
How you change the pack thickness? You buy steel plates of different thickness (as a set or individually) and swap them in / out until you arrive to a combination that you like.
There are plenty of manufacturers that make to order. Talon Engineering, Bespoke Sprockets, B&C Express and many more, your choice. You can also get sprocket blanks that allow you to get them machined to your specs.
Don’t forget I measured the Brake plate to give an approx ID and I could well be out by 2-3 mm?. My measurement of the sprocket bolt holes was also approximate.
Yep, that's probably the way I'll have to go.
Now... more of a concern are the brake shoes. They have stamped on them NAGESTI BARCELONA and Mg (for Magnesium?). No model number or size information on them tho.
They are approx 118 mm outside diameter.
The springs have a funny hookup (first time I see that): they slide in holes in the shoes and are held with cotter pins.
Measured today, the ID of the rear sprocket and hub flange are 120mm and from sprocket bolt centres 130mm. I did not remove the rear wheel for this so I fiddled about with a steel rule. 60 mm from the centre of the rear wheel spindle to the flange or rear sprocket = 120 mm ID
Guess you have definitely got a 348 rear hub, don’t know if the Cappra MX used the same hub.
Brake shoes will be available from In Motion in the UK, I suggest a look online there may be shoe dimensions to help. Saw some 348 parts on e-bay a few months back eg wheels, brake plates and pivots etc.
Good luck with the project? There are more photos of my 348 on the classified ads section.
Thanks for the info. The hub I have has a 130 mm sprocket ID with the bolt holes on a 150 mm diameter circle! So it looks like it's not a 348 hub. I emailed the guys at In Motion UK and they confirmed that they have no sprockets this size. Aaaaaarg!!!!!!
I have this hub that I am planning to use for a project but I am not sure where it comes from. Someone mentioned it might be an old Montesa unit, could anyone confirm? ID for the sprocket is 130mm, I can post additional measurements if that helps.
If it is, where can I find sprockets / brake shoes?
1. Gears.. they exist for a reason - before the coronavirus hit, I was doing a fair bit of practice in mud. I learned quite quickly how important it is to use the gears to maintain grip. Using 3rd when I might be in 1st in the dry, and using 4th (with clutch) for big climbs for example. Now, with an electric bike with one gear, how do you go faster without increasing the torque/power relatively? In general, how do they ride in the slippery clay/mud we have in the south? Having a bike that has max torque all the way through the revs makes it sound like hard work. Gears effectively change the relationship between the torque the engine is producing and what is delivered to the rear wheel.
2. Static/slow speed balance - I'm sure expert riders wouldn't notice a difference but I've been doing engine off balancing for a while and have just started doing engine off hops (mostly because I don't want to annoy the neighbours). Now we know how much easier it is to balance with the engine running, but I didn't realise how much easier front end hops are with the engine on (even without using the clutch at all). With the e-pure, presumably, you don't get any increase in static stability at all? In fact, what is the gyroscopic force of the engine like?
Theoretically with the constant torque of the electric motor, you really don't need gears. Now in practice the motor has a max RPM, so not having gears is a compromise between torque at the rear wheel and maximum speed on the trails. Alta had a motor that could spin up to 14,000 RPM (if I remember correctly) while delivering a very healthy amount of torque, so you could really have both torque (acceleration) at the rear wheel and good top speed. That's not the case on the EM, but in my experience the top speed is plenty enough. One issue tho is when you are close or at the max speed and want to pull a power wheelie over something... That's not going to happen. On the positive side, not gearbox = lighter weight, less maintenance, less failures!
As far as muddy climbs are concerned, not much experience here in California, but plenty of very dry and slippery hills and the EM is pure magic on these. More torque than needed to go up most hills (you'll probably loop the bike or loose traction before you run our of torque), no need to worry about having the slip the clutch to avoid stalling, just constant rear wheel torque with a direct link to the throttle. And you can hear what your rear tire is doing and dial the throttle accordingly. The one thing I haven't been able to do as well on the EM as I can do on the Gas Gas is to synchronize weighing the rear suspension (to get traction) while blipping the throttle. But I am sure that if I work on it for a day that'll come.
Balance - I am not that great at static balancing, but I haven't seen much difference between the Gas Gas and the EM.
I am planning to make my own sticker kit for my 2013 TXT pro. It's relatively easy to find template files (free or $) for MX or enduro bikes but I haven't been able to find anything for my TXT in vector format with a precision good enough that I can design, print and make the final stickers.
Would anyone have either a template file (vector graphics would be best, 1:1 size) or know where I can get (purchase?) one? Something like what's below but in vector format:
I received my Tech fork (see above post) and I found a cheap Gas Gas front hub with rotor on eBay to experiment with setup without having to use the front wheel of my current bike.
Bearing wise, I got a pair of cheap 6004 (20 x 42 x 12) to accommodate the 20 mm Tech axle (instead of the 25 mm from the Marzocchi fork axle). The 6004 are 3 mm wider than the stock 6905 (25 x 52 x 9) bearings.
As expected the 6004 bearings stick out from the hub by 3 mm on each side:
When mounted in the fork:
There are three problems with this approach:
The axle now sticks out by 6 mm (2 x 3 mm from the 6004 bearings) which also means 6 mm less thread engagement on the left side fork tube, which can't be good.
The wheel is offset in the fork on the right side by 3 mm (not sure how this affects handling)
The brake rotor is offset by 3 mm to the right side, requiring a spacer to put it back inline with the caliper. Spacers (and longer bolts) could be used on the caliper side, but that's extra parts that will need to be dealt with every time I take the caliper off)
So, the ideal is to get 20 x 42 x 9 bearings either the 98204Y (which are hard to find especially in 2RS and $$$ - like $75 a pop) or, per benbeta23 recommendation get some B20-157 bearings. The B20-157 are easier to find (well not in the USA even tho these are products from a US company!) and pretty well priced at around $10 a pop).
Here is what is looks like with the B20-157 bearings:
And it all lines up with the caliper almost perfectly (it's offset by 0.4 mm to the right but that's an easy fix).
Before I can get in on the bike I need to get an internal spacer. I might have to make my own because since Ga Gas uses 6004 bearings on the bikes with the Tech fork, it means that they must be using a different front wheel hub for these fork.
I'll keep updating this post once I get it all working.
Left wheel spacer 19.57 mm long step to inner bearing 8.45mm to fit tech wheel bearing 6905 DU
Right wheel spacer 12.39 mm long step to inner bearing 9.24mm
hub inside spacer 73.58 mm long outside spacer 30mm long
disc calp small spacers 3.82 wide od 14.97 mm 8mm hole
yoke spacers 40mm forks turned down and made 39mm spacers forks snug fit spacers with a 3mm lip that stops them sliding down the fork and they stay there mint
hope this helps cheers Wakka NZ
Whoa, that's a lot of information, thanks!
So, it looks like you kept the hub the same as for the Marzocchi fork (with the 6905 bearing and internal spacer).
So if I get this right, you have some spacers do step down the ID of the bearings from the stock 25mm to the 20mm for the Tech axle. What I am not sure is how these spacers fit. Would you mind shooting me some photos?
The disc rotor spacers make sense (SplatShop sells a one piece unit) and for the triple clamp (yokes), mine came with a shinny set of CSP that fit the Tech fork.
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New SWM 350 Jumbo owner - a few questions...
in SWM
Posted
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