1972 DS7 The Row Boat

I've been watching it on netflix. Watched the long way round and now I'm on the Ethiopia episode of the long way down. Ethiopia looked like a rad place to ride.
 
I got the bike back together functionally. When I bought the bike the PO had some carbs hanging off of it that came home with me. I didn't know at that time but they were carbs for a RD250/350. They have the 25 pilots and 140 mains. Right now the bike idles fine and will rev out fine if you quickly get them up. Just a slow blip of the throttle and the bike will bog down and sometimes die. The DS7 carbs came with a 40 pilot jet, I don't know if I should go up that high with these carbs or go for the 35's as that seems to be the fix for a RD250 with chambers, y-boot etc. Any thoughts?

I also set the timing per the MZB instructions at 2.5mm BTDC.
 
clem said:
I got the bike back together functionally. When I bought the bike the PO had some carbs hanging off of it that came home with me. I didn't know at that time but they were carbs for a RD250/350. They have the 25 pilots and 140 mains. Right now the bike idles fine and will rev out fine if you quickly get them up. Just a slow blip of the throttle and the bike will bog down and sometimes die. The DS7 carbs came with a 40 pilot jet, I don't know if I should go up that high with these carbs or go for the 35's as that seems to be the fix for a RD250 with chambers, y-boot etc. Any thoughts?

I also set the timing per the MZB instructions at 2.5mm BTDC.

for the record (yep, laziness is keeping me from reviewing this long (though excellent) thread) could you please list the engine mods. I am not familiar with running mzb, but presume the advance curve brings the advance way down at revs. Very important to see what it is on the big end. I suggest (as always) ignoring EVERYTHING until you get the mains determined. My dart throw says #140 mains will be massively tiny.
 
Jp, no mods here. Top end is stock ds7 @ .25 over bore. Stock porting stock heads. 25 pilot and 140 mains were stock for the rd250 and 350.
 
Hey clem,my RD 250 has stock 25 idle and 115 mains and a slide with 2.0 cut away.
I'll be switching to Y boot soon so your jetting will be interesting fkr me.
 
First thing I would want to do is determine the timing at 7000 + rpm. I'd want it to be about 1.8 mm BTDC to start with. I'd start with #25 pilots, but ignore them until I got the mains and timing dialed in. I'd start with #200's and not be pre-convinced they will be rich - though they probably will be. No telling what your pipes will like. Ignore drivability no matter how bad until the mains are correct. Then fuss with the pilots and then the drivability. Slide cutaway was 2.5 stock I believe on the Rd carbs. I might start with the DS7 carbs though. If you use the RD carbs - remember to seal off the oil injector ports with a bit of silicone.
 
According to my notes, DS7 had 182 O-0 needle jets, 40 pilots and 140 mains. RD250 dropped down to 25 pilots which suggests teh pilot jet outlet and air passages are different because the piston port motor should have a lot of reversion and should need smaller pilots, so if you have stock DS7 carbs start with a 40 to play safe and start with a 140 main or larger just to be safe.

A 182 (primary) will be much richer at wide open high rpm running than a 175 (Bleed), so you may need a smaller main jet than the RD guys end up with. Start rich and work down. Jets are much cheaper than pistons...

JP is right that high rpm timing is more important. I'd expect it to run at 2.0mm but 1.8 is safer with modern gas. 1.85 is where we typically set high rpm race TD3 or TZ250 motors.
 
I don't have the stock carbs for the bike. Don't know if it would be worth buying a set or just tuning the Rd carbs that I have. It seemed to pull fine up top once it got there at around 6500 rpm. I don't know how to set the timing for a particular rpm on the power dynamo iggy. The zeel box could do it.
 
you need some blendzall gold label racing castor octane booster for the fuel just the wonderful aroma as it burns off is worth the extra 50 sents per gallon of gas :) mind you you can mix it much stronger but an ounce or 2 per gallon gits ya the smell of that other planet we used to live on
i also use it in my 4 strokes ,instead of or as well as getting looks, people be sniffin' at you too ;D

http://www.motorcycle-superstore.com/12607/i/blendzall-gold-label-racing-castor-octane-booster
 
You should be able to use a strobe light. Pretty sure the Ds7-R5 alternators are about the same as the RDs and have two notches on the outer edge visible through the opening near the top where the brushes mount. The ones I have checked on RDs are very close to the 2mm BTDC stock timing. The notches should be at 12 o-clock for 2 mm, so if you set them to align at 12:10 - 12:15 you will be very close to the 1.8 safety zone. It would pay to slap a degree wheel on there and make your own marks at 1.8mm so you have a reference you are certain is correct. That is what I do on Rds that use the stock alternator rotor. By the way - spending much time at or above the 8500 stock red line will eventually cause the rotor to shake itself to bits. I have had several rotors that tested fine on the bench but became open or shorted circuits when spinning. When it fails you will have no warning except you will be running on battery until it runs out - then you will be pushing! Can't recall if the MZB is just the ignition or is the whole charging system.

Blendzall. yup!
 
MZB came with permanent mag flywheel reg/rectifier, coil and cdi.
I used to run Klotz 2t oil with c12(I think that was the name) race fuel on the motocross track. It smelled like cotton candy. Don't know if Klotz still makes any oils that are good.
 
Ok, so all you would need to do is slap a dial indicator in one of the cylinders, set the crank to 1.80 mm BTDC (or whatever you wish), and make a mark on the permanent magnet flywheel that lines up with another mark on the engine case. Done! Run the motor with a strobe light connected to it, rev it up to 7 grand and adjust the iggy to make the marks align!
 
I don't have a strobe to check the timing but it was set with a dial gauge per the manufacturer specs.
I installed larger pilot jets(35's) and that took the bottom end bog out. I think that I may have to go through the carbs again and make sure that the slow circuit is completely clean as the air screw is not doing anything when turned in or out. Fun Fun Fun.
 
Hey clem!i dont know if your carbs
are 100 per cent similar to mine (2R8 RD carbs,mikuni 28ss) but i had a similar problem.

There is a tiny air passageway which was blocked.look into the venturi of the carbs (motor not intake side) it is positioned before the oil injector bore on the bottom.
Use a syringe with a thin needle with carb cleaner and afterwards air to make it meticulously clean.
Ultrasonic cleaning doesnt do s**** to this passage :)

This passage messed with my starting and idling pretty bad.
On the pic you can see it in the background behind the needle jet hole.
 

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Ryan, I did look into that inlet. I have a clear path from there through the air screw and into the venturi on the other side of the slide. I took the carbs back apart today to recheck everything. I put them back together turned the petcock on on it immediately flooded the engine. It was too hot to take it all back apart so I said to heck with it. I did put the decals on though.
 

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