DRM 400

[TT5 Matt]

i remember selling 34mm TT500 carbs to the 370 boys years ago and they liked the 4mm up grade and being from the same family of mikuki they fitted straight on with no mods at all,no one ever bothered rejetting and they seemed to work well could be a hassel free cheep up grade

[gavin]

Sounds promising!
Except my 34mm is off a PE175. Would you know where I can get those jetting specs for the TT500?
I'll have to get some before and after pics up soon.

[mposs]

Don't know if this helps, but have copied part of a DR370 Engine hotup article from Nov 1978 Motorcyclist mag. They took the engine out to 450cc and this section was about carburetor specs.

[mick25]

standard 34mm TT500 carby jet specs are 30 pilot 210 main 6h2 needle

[gavin]

Awesome!
Thanks all.
Should save me a few $$ on a 36mm carb. Now I'm off to the garage to start pulling the old DR apart. Got to be better than sunday afternoon TV

Spose I'd better consult the masses on a colour scheme. Currently white with a blue frame. although may strip and polish the alu tank.
Options are:
1. RM yellow and black
2. Blue frame with white plastics (the wheels I have are anodised blue rims as well )
3. Hot rod style: Red frame and silver rims and tank,with flat black everything else (ey wonder if I should whitewall the knobblies )

What do you reckon?

[mick25]

Gavin white wall knobblies cool NZ hot rodders will love that , i reckon yellow RM colour and blacks the go blue rims,  Ive got a DR500 white & black with black rims kiwi built to go hard bro, choice one cuzzie, cool, thats mint, sweet as, howzit, miss those kiwi words good luck send me your email and i will send some pics

[cloggy]

The standard DR370 32mm and DR400  33mm slide carbs have an elongated throat [it's a lot taller than it is wide] so it's difficult to know how they flow compared with an aftermarket 34.
Also the DR400 engine was beefed up a bit  in [if I remember correctly] both the bottom end and gearbox.

[gavin]

Whilst I have the bike apart I will give the motor a full service. Valve clearances, rings, maybe a piston, and some fresh oil and filters. I will then try it with both the std carb (33mm) and the 34mm (now I have the jetting specs ).
I'll let you all know when I eventually get to the test run stage. ::)seems like a long way away!
I'm not looking to hugely boost the HP with cams and headwork, just looking for a nice stong, smooth motor. I'm going to focus more on the handling and weight issues.

The std flywheel seems HUGE! has anyone here tried lightening it at all?

[oldfart]

Gavin, most of your power gain will be in a little bit of port work - 3 angle valve seat - new valve springs .
Put a custom pipe and YOUR STD carb re- jetted and you will have more power than you can handle 
lightening your fly wheel will give your more top end revs with a loss in bottom end torque.
Most of my overtaking are at corners ( engine braking unreal hardly use the brakes ) and on the exit low down torque while short shifting up thru gears 

[cloggy]

Thank you Old Fart,  a larger carb only makes sense with a radicaly modded motor, but it's a persistant myth that a carb on it's own  makes a big difference.
The difference tends to be the carb finally working at high revs  after underperforming everywhere else, hence the power step.
The stock DR is unbelievably bunged up as standard, hence when modding the carbs to adjust for intake and exhaust mods I've always had to jet down, opposite  the norm.
The Suzuki manual is very clear on a 3 step radius at the valve seats.
Have you removed the weird weir in the head's intake or have you left it alone? I'm soon putting back together another motor so  I'm interested in your experience  on this.

[oldfart]

Wier is removed  exhaust port at head radiused - plus material taken away from Valve stem guide .
Your spot on with carby jetting .....better results with jetting down = equals better power curve

When you get closer to make head mods send me a PM

[bazza]

put a 36mm pumper that ray ryan donated on my original DRM,only had to change main jet and not a miss to be had,also lightend the flywheel for bit more snap and motor still pulled like a whalan school boy
Bazza

[cloggy]

Not saying it doesn't work well Bazza, just that it's unlikely to be any better overall than a properly tuned standard carb.
Manufacturers aren't dim, they put on the correct size carb for the engine in the first place
Top OZ tuner of XT 500s uses the standard  late model 34  carb.

[bazza]

36 flat slide ( i found jets i used) was with lighten flywheel, 3 angle valve job,big exhaust and lite porting,with very mild cam.All up a great package.Only sold because to many toys and the Shelby motor was ready to drop in the Muz.

[cloggy]

We've talked in the past of the difficulty of finding suitable fork springs when using 38mm forks
I've now done 3 rallies [UK forestry events for muppets and smokers, -and good blokes on HP2s] and the Norman Retro Enduro. I've got the heaviest Maico springs that were available for 38s [not the same as 40mm springs]. I reckoned that they were supposed to be somewhere around 28lbs per inch, give or take a lb. They've been just right with no preload and no air in 1981 RM125 38mm forks. The Cartridge Emulators have got rid of the spiking.
I went to watch Farleigh castle international twinshock and a Jean-Francois turned up on an immaculate DR engined RM  with Fox shocks and Simons forks, and a 38mm carb on an otherwise bog standard engine. He bagged around 7th overall over the two days. He bent both axles on the jumps though.
He altered the chassis with GN400 bottom frame tubes.
http://i694.photobucket.com/albums/vv306/clogy/farleigh09029.jpg