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Old 11-07-2011, 10:43 PM   #21
lha
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Lha....unfortunately no. Since the stock DT400 pipe is actually a "decent" pipe and Yamaha made the pipe as an expansion chamber...so the "sleeper" mod is not applicable to that pipe.

The 1973 and earlier pipes appear to be designed with performance secondary and looks and contouring to the bike as a top priority ....the internal cone I fabricate and install makes the pipe perform as an expansion chamber and you get the "supercharging" affect.
Dang!!! lha
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Old 11-07-2011, 10:48 PM   #22
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Look closely.....you can see the tip of the spark arrestor has disintergrated and is paper thin...and I have started to cut this out.
We will fabricate a new section and it will be as good as new!



You also see the verical supports that needed to be cutaway to get the pipe open. A portion of the internal mesh will need to be cutaway to make way for the sleeper cone. This pipe is in need of some repairs but should work out just fine. The rest of the pipe is pretty solid.
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Old 11-08-2011, 01:14 PM   #23
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Here's the newly fabricated front portion of the spark arrestor assembly



From this view you can see the portion of the inner liner that has been cut away. The factory tack welds the mesh in several places.... fortunately the mesh is made of soft flexible metal that allows it to be pryed away from the pipe and then cut using metal snips.

Those remaining strip of metal underneath the spark arrestor will be removed before the "Sleeper Cone" is welded in place. Unfortunately there is no quick or easy way to do this type work.....so you have to take your time and work carefully not to damage the pipe of cut yourself on all the razor sharp edges everywhere.
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Old 11-08-2011, 01:39 PM   #24
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This is excellent documentation....
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Old 11-08-2011, 06:10 PM   #25
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This is excellent documentation....
Not to mention the mondo improvement over the stock pipe!
Excellent research and development Dave!
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Old 11-09-2011, 12:29 PM   #26
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Not to mention the mondo improvement over the stock pipe!
Excellent research and development Dave!
Spending time playing with different cone shapes and sizes and locations within the pipe has paid off. I think a "sleeper pipe" will really take your bike to the next level of performance. I have been very satisfied with the performance results.....and best of all you retain the stock look of the bike which I think is very important.

Lbrandy took delivery of his "Sleeper Pipe" we should be hearing from him soon on how his pipe is working !
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Old 11-09-2011, 07:05 PM   #27
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I just made the trip out to D & D SLEPPER PIPES R &D Headquartes to pick up my pipe #5 of the first run . Had a grin on my face all the way home . Could not wait to get the pipe on the bike . it bolted right back on .2 kickes and we were off . The sound of the pipe had a nice little pop. The pipe makes the bike run better threw out all the powerband . and also will pull a few more rpms. nice job guys. LBRandy
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Old 11-09-2011, 09:19 PM   #28
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Thanks Randy...glad you like it.

I think once we get your timing set correctly you will have even more newly found power!
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Old 11-12-2011, 04:49 PM   #29
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Default Sleeper Pipe #5

Here's Randys Sleeper Pipe #5.....aka SP5


Finished in a semi gloss....



Randy brought his bike over yesterday...we used a dial indicator to set his timing tab and set his timing to factory specs... Then went out for a ride. We rode highway and some pretty technical stuff in the dirt. The first thing I noticed is his bike now climbs like a mountain goat ! On steeper hillclimbs Randys bike used to have trouble....with the new pipe the improved low-end power is very noticable ! He had no trouble climbing anything yesterday and he is running 1 tooth higher on his counter tooth sprocket.

Each Sleeper is tagged with an ID number for future reference...so I know what style cone is inside. The SP5 is fitted with a midrange cone optimized for the DT and is designed for a power hit about 5k or so but also improves power from idle to redline.
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Old 11-12-2011, 04:55 PM   #30
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Went on a nice dual sport ride with the boys from D&D SLEPPER PIPE yesterday. But first we, or i should say they set my timing spot on. The first part of the road ride you go up a nice steep climb . I have been up a few times but with the SP on i could pull 5 th gear. When we got to the flat roads it just seamed alot smother over all. But the best part was when we got to the off road part. We went up some up steep rutted an rocky hills. I was a little worry because i was runing a tall gear on the front. But with the SP on it pulled it with no problem. Thank again guys . Now off the the shop to do some port work. Randy
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