Dr Big rebuild/restore

Questions regarding the DR750

Dr Big rebuild/restore

Postby CapnNogrow » Wed Aug 02, 2017 7:37 pm

IMG_1218.JPG
I bought my big a year ago disassembled. The previous owner had bought it as a project and "didn't have the time" to finish it. That often means a loss of interest or loss of knowledge, or both. He'd sandblasted and resprayed the frame in a solid black colour, and restored the old swing with new bearings and a spanking new shock absorber. Yay me! Now, the original SR41 -89 sports a 750 engine. But unfortunately the cam had taken quite a bit of damage due to low oil level. So he bought a dr800 engine and some parts from a -92 and fitted it to the frame. That's where he lost interest and I saved it. I worked for a couple of months reassembling the bike. I did had to buy another used camshaft because the one in the 800 was cracked.
When finished I ended up with a dr 750 with dr 800 engine, manual decomp, Dr 750 camshaft and a bike that ran like shit. I nearly tore my hair out over it, even consulted the forums. Turns out the previous owner thought the CDI from the 750 would work perfectly with the 800 engine :roll: .
Now it's running damn near perfect with its new Lazer exhaust. Only thing left is opening up the airbox.
I also renovated the front and rear brakes, front fork, gave it new blinkers. Have mounted a Kenda Big Block as front tire. (Wiped out when the old one got a puncture coming down a mountain, scraped the tank and busted up my knee) Tell me what you think about it. Possible must have modifications? Suggestions?

Future plans:

1. Open up airbox.
2. Replace leaky left side motor cover (stator side)
3. Fix and respray the tanks and add new decals.
4. Fit the choke in a better place than duct taped to the steering bar.
5. Possibly some tank and motor protectors.
6. New rear tire. Michelin Anakee Wild.
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Re: Dr Big rebuild/restore

Postby DHC6 » Wed Aug 02, 2017 11:21 pm

If you have got the 750 engine with it swap the primary drive (crank / clutch), install a new oil seal in the RH cover at the same time. Get rid of the airbox and get a KN filter or like wise and make an airbox out of roof rubber sheet. Tank bars RD moto. Front fork stabliser http://dr-big-shop.de/BIG_Fahrwerk_263.html,
Service the front fork and find 1/2" or 12 mm front brake cylinder, with sinter metal pads it than really brakes.

Good luck with this nice project.

R
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Re: Dr Big rebuild/restore

Postby Deano » Thu Aug 03, 2017 7:55 am

Good work :tup: it is nice to see another back on the road and not been cut up to make a café racer/bobber out of it. It will always be appreciated on this site.
I have my wife's permission to keep breathing!!
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Re: Dr Big rebuild/restore

Postby BigBob » Thu Aug 03, 2017 8:48 am

The 1990 800 used exactly the same electrics and CDI as the 750, though the later 91-on 800 used a completely different system, and as you say, will run like shit
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Re: Dr Big rebuild/restore

Postby CapnNogrow » Fri Aug 04, 2017 4:42 pm

Oh it ran even worse when my failed homemade exhaust broke lose from the muffler. The BIGs don't run all that well with straight pipes. :D
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