DR400 mods

[GMC]

I have heard a couple of reports of shock shafts snapping because of the extra vibrations of having the balancers removed.
One was on an XT 600 that was ridden on the road, snapped the shaft a couple of times.
Another I think was a Husky 610 in a road bike frame that was road raced, it also snapped the shock shaft a couiple of times.

[YUMASTEPSIDE]

to remove or not to remove- that is the question.
whether it is nobler in the mind to suffer the vibration of the handlebars or to bear the slowness of accelereation.......sorry, I digress !!

.........so, remove or not ??   

                        Roger

[mick25]

I have a dr500 and while the gear box was striped and getting rebuit, i had the same idea to remove all the moving bits of the balancer it all came to around three and half kgs in weight so its a fair bit of weight, but when i asked my local bike mechcanic he talked me out of removing them ,and i throught any way they were put there for a reason ,
when i had my gear box apart the gear dog from second gear was broken off,second and forth gears have smaller dogs than others ,TT500 ones are twice the size...
I dont no how mine broke it might of been a week make or push starting (SOME THING I DONT LIKE DOING ON 4 stokes because of extra strees on these parts) or persons rough usage
 IT made me a bit worryed 
because i use second gear on race starts, but saying all this i havent any probs for the last 4 years thats my 2 bobs worth

[cloggy]

 If you see Tom White every weekend, ask him if he's got the jetting specs for the 36 Mikuni he used to sell for this model. He was kind enough to send it to me decades ago, and I've lost it.
The key to making these old motors go is to get more torque out of them by modding intake exhaust and getting different cams [cams make a difference on the DR but although Mega Cycle have the profiles and and R & D have the springs, the keepers are no longer available from R & D]  ie getting more power per rev, not more revs
 Also they're a bit slack on the front end. They tightend the head angle by 1 degree back in the day, not that I've done this. However I have run short front forks and long rear shocks and it never got anywhere near unstable
 The back wheel is real heavy. You lose more weight changing that than adding an ally swing arm.
There was a DR at Farleigh this weekend. It was running 81 + RM rear wheel assembly in a PE or RM square swingarm
 [The UK is pretty informal as to what one can use on twinshock compared to the USA or OZ]
Problem is you end up with a very high seat and a very short overworked shock. The DR frame has the shock mounts set further rearward than the RM. You really need a custom shock to fix that. That could cost as much as the rest of the bike! Or just relocate the arm shock mounts.
 Best ally arm for these is a KLX250 or a 78 RMC round ally arm. The latter you have to weld up with ally tube inserts inside the ends of the swing arm pivot {+ slightly wider] That gets rid of the weakness on that arm and lets you use all the DR pivot pin gubbins. They aren't any longer than the standard arm so it's a lot of cost  for just a bit of weight as you have to use slightly shorter shocks. If you haven't yet got decent shocks then it makes more sense. Stock arm needs a 16.5 " shock with  a 4.5" stroke
The RM needs a 400mm arm. I think the KLX needs much the same.
There is possibly one more option. The later DR500 is supposed to use an ally arm dimensionally identical to the 400's steel arm. Apparently they originally designed the 400 arm in ally but made it in steel due to cost. That is your best bet if you're in the USA. UK never got the 500. Another recession saw to that.

 

[oldfart]

Cloggy, Most of the USA 1983 DR 500 came with alloy rear swing arms - and yes they are a straight bolt up fit.
I have had a great run with a pair of piggy back shocks off the same model bike ......spring rates - travel - and length are spot on.

[cloggy]

 There has always been some confusion as to whether 500s came with ally arms or no. Thanks for that. Did the SP500 have just the steel arm? I have a feeling that the SP may have had a pretty much identical frame, engine and swingarm, possibly wheels too.
Do you mean that you're running the 500 arm in the 400 frame?
There is a lot of commonality between the 400 and 500 and I assumed the 500 arm to be dimensionally identical
 I'm running Ohlins  16.5" shocks on one road going DR. It came as a rolling chassis with them. They are off the Armstrong/Harley 500/350 Rotax 4stroke Three ex army guys were racing them at the Farleigh Castle international meet last weekend. They were far from last too!

[EML]

The 400 model was suposed to be identicle to the 500 except the Japonese had a 400cc upper limit for that range of bikes.
If you look across the range the home market had 400s in every thing i.e. XT/TT XL/XR DR/SP etc...
It was their way of limiting riders though how you can get hurt on a 500 but not a 400 is a question to be asked???

[cloggy]

 Yamaha did a 400 version of the 550 and the 500 which are totally different bikes. I hadn't heard that Suzuki had done the same with the 500 4 valve, though it makes sense.

 There's a 400cc Test limit in Japan. To ride bigger bikes one has to take a much more involved test/racket for [ex policeman] instructors. If you don't take loads of lessons you are failed by their mates the testers.
 
The bike that predated the 500 was initially the 370 SP/DR. That was beefed up and made into a 400. It just had 2 valves no bancers, and doesn't have the same frame mounts.  Lots of UK people think it is a 4valver due to TBM's bike guide being pants.

[oldfart]

In my eye's the the Dr  400 biggest problem are  cam jornals flogging out. Dr 500 are way too Friggin heavy.
Cloggy, front and rear wheels also interchange along with tanks.
I am running a 1978 c2 arm on my  DR 400 -  and have a alloy arm fitted to my  DR 500 ( same material used on  Pe/ Rm 1981 models ).......and yes they also fit Dr 400 to answer your question

[LWC82PE]

The American 'enduro' spec 500's  X, Z, D etc had alloy swingarms or were at least ment to have them, there could have been a couple of steel armed ones slip theough.

The rest of the world generally had the trail version which was a lot different. These were the 'S' models so SX, SZ, SD etc

The SP500 is basically a trail DR500 'S' just re-badged as a SP in USA as they called them a SP500 as to save confusion over having 2 DR500 models and one was called a DR and one called an SP  to differentiat between enduro an trail models.

So yes the SP500 had the same steel swingarm that the worldwide 'trail S' DR500's got.

[oldfart]

Take note  ... of RHS view @ rear of swing arm ( note it is hollow ) also type of shock used.       This should explain what Leith and I are talking about
http://www.youtube.com/watch?v=D28OXHDhIxA

[LWC82PE]

That was a good video shows it well. Note the piggyback shocks and PE type forks. The trail version didnt have the PE type forks with the forks extending down past the axle or the piggyback shocks.

There would be plenty of DR pics on

http://www.bikepics.com/

and

http://www.suzukicycles.org/

and if you do a general 'google image' search

[cloggy]

 Mystery Resolved!
 Thanks very much for that
 UK only got the DR400s; no t and no 500
 The 500 engine must be a very heavy lump, cos not much else changed
 I've got 5 or 6 heads, all ok. Never seen a knackered one but we don't get the heat, or the distance.....
Scroll down near the bottom for the third placing 1983 DR500
http://www.dakardantan.com/forum/photos-paris-alger-dakar-1983-vt1006-30.html

[LWC82PE]

There was also 2 DR400's. There was an Enduro 'T' model and a Trail 'ST' model. Being in UK you would have only got the 'ST' i reckon. I have read somewhere that some countries continued to get DR400's in 81 but im not sure if thats 100% true.

In Australia we got a few Enduro spec 400/500 DR's but they were generally specially imported in limited numbers by individual dealers who wanted them. They were mainly ment for the north american market. They didnt have compliance plates and were not road registerable in Australia but a few non complianced 'enduro' DR's did manage to get on the roads in a few places, most likely illegally (getting a compliance plate off a trail version etc)

[lukeb1961]

nice looking bike.