Messages

just a thought. make sure the slide aligning pin isnt pushed out some on the other side of the carb. if it is.. this will allow the slide to rotate in the bore. Not nec saying thats the issue but worth looking at. 

All good there, though I just found out how easily the locating pin can be moved. 

I think I'm just crazy and looking at it from an angle. I'm just not sure what else would limit the revs as long as it's not the throttle limiting the pull.

Won't rev out? That's not normal. Even on a rich bike, it should rev out, only in the high top end at speed will you get garbled running (when rich).

Too lean, well the bike just won't like revving. OR, consequently it will like revving so much it goes pop. Lean is mean... they say.

I'm looking at the carb sync section in the Haynes manual. The picture doesn't match up with what I'm seeing. The dimple on the slides is offset from the portal, so I can't tell where it should be on wot. In the picture, it's centered with the bottom of the dimple aligning with the bottom of the portal.

So maybe it's a cable adjustment issue? I can also go back up on the main to enrich it a bit.

Are you saying that you can not see the dimple in the sight glass on your carbs? Are your slides in the correct way around?

The slides are 100% definitely in the correct way (I made that mistake already a few months ago)
What I'm saying is the dimple isn't aligned with the center of the sight glass. It's off the the left, so at wot, the 7 o'clock position of the dimple meets the 7 o'clock position of the sight glass. I posted a pic a little earlier with the dimple raised up a bit to make it easier to see.
In the pic in the manual, the 6 o'clock position mates up with the 6 o'clock position of the sight glass. I hope that makes sense.
But the slides are right way round. And they slide in along the guide on the carb just fine. It's just the dimple is off to the left on both carbs. Oh. It's possible they're not the stock slides. I'd have to look at past posts to find the part number.

Semi old gas shouldnt matter much if everything is right, I was thinkin float height or actual delivery to the carb.  Make sure the pipes are clear, the popcorn machine is usually pretty obvious if one isnt firing or flowing and they are pretty slow on 1 cylinder.

Only a couple screws to check timing too if just to see if it looks about right.

Slides reversed? I forget how that acts. They do run okish with the crossover tube off.

Lol I screwed up and reversed the slides during the rebuild. I double check every time now. I can check the timing again now that the coils are fresh. I believe I have it set at 2.1mm btdc.

I dont think mine is even interesting until above 5k and you can pretty much ham fist it from idle and only winds up a bit, Dave F, 160main iirc, stock pipes/cylinder, crossover.

I'm thinkin u got something else goin on there. Certain you are getting fuel?  Fresh, clean fuel? Certain the carb pieces are correct? Center tube things cleaned and installed all the way in for sure?  Needle mounted correctly? No monsterous air leaks?  Exhaust and air filter clear for sure? Pistons not backwards?(I forget what this does)

Just some suggestions down some other paths, GL

Yep. Tubes are new and installed correctly. Needles are, too. I just cleaned the petcock and replaced the needle valves. Air filter is brand new (30 miles on the bike since I renewed it). I just did the Dave F mod over the weekend, so it's definitely clear there, too.

The fuel is fresh, but could be fresher. I might throw it in my pickup and swap it with some ethanol free from across town.

Next time I take it out (cutting grass aka drinking beer tonight), I'll try going ricer on the needle and main. 250 was toooo rich and fouled the plugs. I'll try 220 again. Oh, and I'll go ahead and pull and clean the air filter because you never know.

Thanks for the insight.

Rob

Won't rev out? That's not normal. Even on a rich bike, it should rev out, only in the high top end at speed will you get garbled running (when rich).

Too lean, well the bike just won't like revving. OR, consequently it will like revving so much it goes pop. Lean is mean... they say.

I'm looking at the carb sync section in the Haynes manual. The picture doesn't match up with what I'm seeing. The dimple on the slides is offset from the portal, so I can't tell where it should be on wot. In the picture, it's centered with the bottom of the dimple aligning with the bottom of the portal.

So maybe it's a cable adjustment issue? I can also go back up on the main to enrich it a bit.

I'm sure my earlier issue was a stuck slide. I don't know how that happened.

I'm now at a 200 main and it's better, for sure. The plug is a nice tan.

But it's still pretty slow. I'm going to raise the clip on the needle one notch above center (I started at center, went one notch down).

The bike won't rev over around 5-5500rpm at wot. To get the speed up, I really need to feather the throttle and it will eventually go faster, but still not over around 5500rpm.

jet tube will richen or lean everything everything from 1/4 up to the main. but yes, it can work.

Is that up to the main or up through the main?

After Chuck did update porting on mine, it is running sweet with this jetting setup, (UNI's - no red outers, boost bottle and FPP chambers):

Aside from the different needle jet, it's a really similar setup to what I have. The p2 should work, though, right? I'm not really familiar with the difference between the p2 and p5. Can other adjustments like the needle clip and main jet take up some of that difference?

I did try to go to a 250 main as that's what SoCal250 is running, but it was way too rich.

the airjets at 6 o clock i hope.

on a  400 you may need a p6.

Haha yeah, the 6 o'clock airjets. I think I had a stuck slide, causing the performance problem on the test ride. Going to get back at it tomorrow. Hopefully the p2 will work.

Drilled the airjet to 5/64" and now there's a severe lack of power throughout the throttle. I could barely get it over ~35mph and on the hill it struggled to the point where I was worried it wouldn't make it up.

Does it sound like the two are related or it there a better chance I messed something else up? I didn't swap any jets or the needle position while I had the carbs off.

you should drill the airjet out to 2.0mm doing the dave f mod. (or 5/64")

I'll give it a try!

I think I'm finally on track with this rd400 project I've been working on. I had to take a few weeks off for sanity's sake.

New coils
New carb setup:
Went from 175-p2 tubes to 169-p2
Went from 5I4 needles to 5dp7 on center notch
Went from 35 pilots to 32.5
Dropped from 220 mains to 210

And what probably made the biggest difference, and I'm embarrassed to say this:
The PVC sleeve in the reproduction rd350 y-boot wasn't seated in the filter, so it was very likely blocking the air flow.

It pulls pretty nice through around 3/4 throttle, but still not 100%. 3/4 to full throttle is worse. The plugs are evenly grey.
So there's still some tuning needed. I have 200, 210, 220, 250, and 310 mains to choose from. When I get some time, I need to ride over to my FIL's garage where I can do a plug chop on flat road. Now that it will actually make it over to the other side of town.

Thanks everyone for helping me through this adventure.
Rob

THATS CORRECT.

You're the man, Mark.

I picked up some new coils from Economy and the product description states:
"We recommend removal/bypassing of ballast resistor on RD400's"

I just want to make sure I have this right. I'm going to connect the existing male red/white wire from the loom to both black wires on the new coils, leaving the three resistor wires disconnected. Then connect the yellow wires on the new coils to the corresponding orange and grey wires on the loom.

Can anyone confirm or correct me?

just fix it 90s style, smear some orange rtv in that crack. lol

neat bikes, never owned one , they seem to eb a love or hate them model. 

Thanks man. We're talking about the "1977 Motorcycle News Machine of the Year" here!

It's my first (and only rideable) bike, so it's pretty much the only thing I've ever really known (learned to ride on it in 2008). It's been a pleasure to own.

I know more than one person that figures if its leaking oil, it has oil, which is much better than no oil

I've dealt with it weeping for so long, I don't remember the last time it didn't. Maybe one of these winters I'll break it down but it's riding season.

And my left boot has a nice shine to it!