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post #11 of 74 Old 03-30-2015, 10:50 AM
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BTW are those gold chains just for the looks or do they have any other perks?

My computer is fighting Aids and Cancer in it's idle time, and yours?
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post #12 of 74 Old 03-30-2015, 11:06 AM Thread Starter
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Originally Posted by Schroeder View Post
BTW are those gold chains just for the looks or do they have any other perks?
Mostly looks I guess, but they may be more resistant to rusting because of the plating than a standard black chain.

I just like how it looks.
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post #13 of 74 Old 04-03-2015, 10:56 PM Thread Starter
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Changed-out the standard bolts for some button heads with internal star washers instead of the crimp plates for a cleaner look -



Also found out that it's a factory 75 and not a 50. That means it has a longer stroke. I was pretty sure from riding it (and how it sounds) that it wasn't a 50.

In the process of modifying the intake manifold to get a smoother transition from the carb to the manifold and into the reed cage.
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post #14 of 74 Old 04-10-2015, 05:34 PM Thread Starter
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This is the "before" shot -


Got it all back together after making a few changes -





I was planning to take it for a spin, but it started raining before I could. I've changed the manifold quite a bit, and richened the jetting some, so I'm anxious to see how it runs now. Still needs new tires, so I won't be hittin' the corners very hard.

Still need to finish the aluminum cover to replace the rear seat (removed all passenger stuff) and plan to powder coat the wheels blue to match the graphics later this season.

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post #15 of 74 Old 04-11-2015, 02:06 AM
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Looking GREAT mate! Man i miss the smell of two stroke in the morning.

Take care & ride safe.

2012 Honda CBR 250RAb, Sold.
2013 CBR 600RR, Sold.
2013 Kawasaki Ninja 650R, Road. (wife's)
2015 Kawasaki Z300, Road. (wife's)
2014 BMW S1000RR HP4, Road / Flying Machine. (Traded in the wife for it)
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post #16 of 74 Old 04-12-2015, 01:58 PM Thread Starter
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Thanks.

I was running Yamalube when I got it, and it didn't smell that great. Changed to Redline ester race oil now and it smells much better! It was set-up as premix when I got it, which is a good idea.

Put a few miles on it yesterday, and it ran OK, but the jetting isn't quite right yet. I need to order a 1 size smaller main and make an adjustment to the needle.

I think the mods we made to the intake manifold helped peak power, as it feels like it's pulling stronger on top now.

EDIT: Got a new float needle and seat, main jet, and a needle jet with a fatter taper (the other was full-lean and still too rich). Also will drop the float level 2mm as suggested by the Mikuni tech. The carb sits at a 30 degree angle into the reed block, which is really too much. 12 to 15 degrees is the recommended max. Not much I can do about it.

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post #17 of 74 Old 04-19-2015, 09:26 AM Thread Starter
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Though U.S. riders may not be familiar with the Derbi name, they might recognize one of its factory riders -



I believe this photo is from Derbi's 100th GP victory in 2010 (Marc Marquez aboard).

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post #18 of 74 Old 05-04-2015, 11:49 AM Thread Starter
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Put about 75 mi on the Derbi this weekend. Finally running good. I had to purchase a new jet needle, needle jet, and main to get it right. Still plan to go leaner on the pilot, as the adjustment is almost max lean. Overall the carb was very rich, and now after leaning it out it will pull clean from idle to redline. Much easier to ride, and not really that slow if you keep it in the 8000 and over range - which isn't that difficult.

Here are a few photos from this weekend's cycle get together in Pine Bluff, WI -



My son rode the Derbi, I rode my buddy's '65 Bultaco Metralla, and he rode his new KTM RC390. I rode the RC390 on the way back.





Almost everything and anything shows-up.

Slimey Crud Run | Pine Bluff to Leland and back!Slimey Crud Run | Pine Bluff to Leland and back!

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post #19 of 74 Old 05-13-2015, 03:02 PM Thread Starter
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Thought I should have a helmet to go with it -

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post #20 of 74 Old 07-06-2015, 11:21 AM Thread Starter
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Put another 70 mi or so on the Derbi this weekend on the backroads of WI.



It's running strong and clean. Looking into changing the gearing, as it's spinning about 9200 rpms @ 60mph. Redline is 11,000. Top speed is rpm limited for the most part, but it could easily cruise at a lower rpm. With the mods it has it is making enough power that the super-low gearing isn't necessary.

Trying to figure out the range. It holds 2 gal, and because it's running premix stopping for gas is a problem. I need to top it off with premix and figure out what the range is so we can relax a bit when out on the road.

Talked to a guy at Road America the other day that was riding a stock Aprilia RS50, and he says he is pegged at 55 mph.

My son has been riding it most of the time. He's 19 and about 130#, which helps. Everything makes a difference, and just tucking down behind the windscreen gives a noticeable rise in RPMs when cruising.
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