DIY Monster Scrambler

[koko64]

Some M750's are going cheap and actual Scrambler models are very expensive here. I keep coming back to building my own due to cost and the simplicity of carbs. 16.5 litres of fuel is useful too. The biggest issue is if one were to use the stock suspension, how much is required to extend the fork stroke say 30mm. The bike would be used for rough back roads, dirt roads and easier trails.

The rear can be raised with longer heim joints, longer or extended stroke shock and custom chain tension wheel. Say 140-150mm travel. The front is the issue for me. I would use the stock wheels with TKC70's or MT60R's.

Any thoughts?

[Howie]

Superbike forks are a little longer.  I'm not sure if this would give you 30mm.  This would require new or modified triples.

[koko64]

Cheers Howie.

I note that 620's have 148mm rear travel and 130 front. 148 up back will do fine and 130 mm up front is a start. I reckon my local suspension place could get another 20mm and drop the forks through the triples 20mm to compensate for front wheel clearance. Although injected base 620's (not 620L's) are coming down in price, have 15 litres, are not over braked for the dirt and are pretty simple for an efi bike. Meanwhile, the unloved 750's are getting quite cheap while 600's, 659's, 620L's and 400's hold their value as compulsory learner bikes.

I no longer require a Multi with bags as my pillion in a million cant go far due to a long skating career catching up with her. Something for exploring from a central point ala scrambler works fine. Scramblers run 9-14k for an Icon here, which is pretty fancy for a holiday runabout.

Any thoughts or tips?

[stopintime]

MultiStrada fork?

[koko64]

Hmmm. Thanks Lars.

[Howie]

750 should be a great Scrambler engine.  Flat torque curve.

[koko64]

Yeah I figure a 750 will be enough for the task. The dream of big touring with the GLW had to be replaced with exploring from a base camp. Since I no longer need big cubes for touring a pretty stock 750 motor will be fine for sight seeing and trail riding. A smaller, lighter bike would be easier for the trails anyway.

[d3vi@nt]

There are a handful of threads over at ADVRider with folks who have done/attempted enduro conversions. Might find useful information looking up the Terra Mostro project (now defunct), as well.

Seems like a fun project 

[koko64]

Cheers D
That was the first thing I did. Those conversions certainly show a committment to serious dirt riding and great backyard engineering, but my plan is quite half arsed by comparison.

[Speeddog]

43mm Monster adjustable Showa front fork can be fitted with SBK cartridges, gives ~20mm more travel.
The set that I'm currently running has about 145mm travel.

Small case motors have ~12mm shallower 'sump' area on the cases, so more ground clearance than the big blocks.

Need to get the exhaust pipe from the horizontal up out of harm's way, and protect that oil filter.

[koko64]

Thanks Nick

Didn't know that could be done with those forks so a 2000+ model 750 suits

[koko64]

Does extending travel work on the older 41mm forks and do non adjustable qualify? My suspension guy can do just about anything for a price, so quick and dirty mods are preferable.

Regarding the rear I thought that my local suspension guy could work the shock or a 620 shock and I run longer heim joints to get another 30-40mm travel out back.

[koko64]

M750 prices are falling here. Going to check out a 2000 M750 in Yellow.
Been looking at tkc70s, Avon Trailriders and MT60rs and Scorpion Trails. Here TKC70s are nearly $600 a pair, Trailriders are about $440 but an MT60RS front and Scorpion Trail rear combo is about $400. Any info on these tyres? I've read reviews but anyone here have FHE? Sizes would be 120/70/17 F and 150/60-70/17 R.

[stopintime]

Don't know if they fit, but the superbikes often got new flat suspension rockers to deal with the unwanted progressive linkage. They usually (?) changed the rod to match the new rod/damper attachment height. If you could fit that type of rocker without the new rod, you'd have new height without the massive amount of progressive linkage from very high joints.

[Speeddog]

There's a performance crossover compromise on Monster based ADV bikes.

As the forks get longer and the swingarm angle increases, weight gets shifted backwards.
That reduces the cornering limit in the dirt, makes it prone to folding the front on corner exit.
Doesn't really help street performance either.

They also get soft in pitch, tend to not want to finish corners, especially uphill ones.

So it's useful to get ground clearance by getting the pipe up out of harm's way rather than jacking the bike up higher.

Basic geometry of the Monster is pretty good for what the bike is intended for.
Pushing the envelope too far requires mods to help it all work (like most anything  ).

I've run with an Ohlins rear shock using a new (shorter) seal head and minimum spacers such that the rocker nearly touches the tank bracket on my '98 M750.
I've run a swingarm that's 2" longer.


I've got no info on extending travel of the 41's.

There's a good bit of 50/54 outer diameter forks out there, there may be something from another application that's good.

One thing to watch out for.... the early hyper forks looked the business, but were in effect, shortened off-road forks.
All that was good, but the method left too little room for the spring.
Physically couldn't get a stiff enough spring with 'normal' spring wire without coil bind.
All of that may be old news, ask your suspension man to see.

Have zero FHE on those tires.
I've run TKC80's a bit, they're good off road, feel squirmy on road, and wear fast.
I may try some Shinko 705's, those look to have some dirt capability but not be too bad on road.
ADV guys seem to like them.