Just got my bike running, need to bounce some ideas off forum members

[rdsarefun]

I purchased a 75 350 late March (stock bore, someone had put a set of DG pipes on it, stock carb and jetting).  Before tearing into, I put a new battery in it, had spark and then performed a leak down test.  Passed the test (lost 1 psi over 6 minutes), a little tired but will tear into this winter. I put a boroscope in the plug and exhaust hole, little carboned up and some scratches but it sealed and held pressure, again will address this winter  I freshened up the bike with new tires/tubes/rim strips,chain and sprockets, rebuilt caliper, new master and brakes put new rubber and cables on it, rebuilt the carbs and performed the Dave F carb mod (with 200 mains, 5DP7 jet needle, 169P0 primary needle jet, 27.5 pilot, air screw 1 turn out and needle clip in center position).  Upon first trying to get it to run, would backfire thru exhaust.  I reset the factory points to .013" and after swapping the coil wires (found out that the laminated wiring diagram I have has the coil wires reversed),it fired on first kick. Smoked a bit but finally warmed up some and idle settled down to about 1200 rpm, I timed it with a light at 2.00mm. and then started to turn the airscrew out to 1.5 turns each, rpm a little higher when I did this.  The bike is just flat,does not want to rev and I noticed raw gas coming from exhaust when I shut it off.  It has the factory airbox, although a UNI foam filter within that is oiled.  I removed the carbs, and dropped main jet to 190, moved the needle clip up 1 space (2nd from top) and checked the float levels, these were a little high so reset to 15mm.  Put it back together and a little better, but not much.  Definitely not rideable.  I do have a new Dyna S ignition coming today, wanted to get it running with points before I put this on. Looking for some suggestions.  When apart, checked the coils and within spec (original) and put in new plugs before trying to run.  Thinking airbox may be too restrictive, thoughts?  Plans are to bore and mildly port, leave everything else "as is" as this is just a cruiser for weekend runs thru the park and scare the wild animals. 

[LMS]

The experts will chime in, but I have the same bike but with a tad more mods, not much though and I'm a rookie. But from what I have read, etc... with the jets you have in there now, it's way rich on the main. Check this out as an example. Get a Y boot and K&N, or a uni to go with it.
https://hvccycle.net/carburetor-jetting/
Might want to time it at 1.8 as well.

[m in sc]

yeah the Dave f mod is for a large k&n in a y boot or a set of uni foam filters.

[rdsarefun]

I am looking into a new Y boot and a K&N,but have a few questions.  Will the K&N filter fit on the factory Y boot, or is the "kit" specific by having a slightly different Y boot?  I ask as this is the only RD that I have owned where this boot is soft and pliable, others hard as a rock and needed the wintergreen oil treatment.  Additionally, I am thinking of putting a different set of manifolds on with a crossover tube, I looked at an old invoice I had from Chuck Q, he sold banshee intakes, is this direct bolt on and is anything needed for the reed cages? I have read where individuals have cut and modified these banshee intakes, trying to get solid info as searches vary in content.  Just trying to put together everything at once to get the bike running and have some seat time.   

[1976RD400C]

Seems way too rich to me. More like a 150.

[m in sc]

you can just get the k&n but you need the compression ring as well. you might be under a 150 main w the stock airbox since the jet tube will cause it all to run rich.

for example:

stock carbs on your setups will be around 150 w dg pipes and a stock airbox w a uni,

stock cabs with airbox/uni but lid off will be 170-190 main jet

stock carbs with a K&N and y boot with that setup will be around a 230-250 main (no airbox)

dave f modded cabs w a k&n in the y boot is around a 190-200 main

all foam unis will jet about the same as a k&n and y boot fyi. i would suggest you get  a set of all foam unis since the carbs are already modded and take the stock airbox out

 

as far as the intakes w the crossover, they def wont hurt but arent going to cure it

[rdsarefun]

Another weekend, more time to work on bike. Bike is stock bore 75 350 with DG pipes.  I ended up ordering a K&N with a new Y boot from John @ Economy along with some more main jets and a new throttle tube.  I put everything together and have the carb currently (set up with Dave F mod)5DP7 jet needle, 169P0 primary needle jet, 27.5 pilot, with 200 mains and the needle clip in center position, air screw 1 turn out from seated.  Upon startup the bike raised in RPM's to 4K and idled at this value. I turned the air screw on each carb out to 1.5 turns from seated and the RPM raised a little more, as expected.  I then turned these back in to .5 turn from seated and the RPM dropped a little, but still around 4K RPM.  A little info prior to starting bike: I had the carb slides bottomed out and I checked these with a boroscope thru Y boot prior to startup and have these set to 1/2 turn from where they started to move upwards using adjustment screw.   I could also see both slides raise to the top and fully seat by using the throttle.  Was thinking could be cable hanging up, I took the adjustment out of cables regardless with no change.  The carb slides have the cutout facing the rear and the bike was leak down tested prior with no issues.  I was then thinking, OK this has to be an air leak.  I sprayed the reed block, carb (i.e. all connections downstream of the air filter to the cylinder, spark plug holes and exhaust flanges with starting fluid looking for a change in RPM, nothing.  So I can only surmise that the bike is getting too much fuel? Thinking of dropping main to 170 or 180 (I have pairs of jets from 170 thru 220).  If an air leak, starting fluid would have found path, any thoughts?

[m in sc]

main jet will have zero to do with idle, or mid range throttle.  when you did the dave f mod, did you drill the airjet out to 2.0mm?

can you drop the slides w the adjustment screws enough so it wont run? if you cant, then the cables need to be addressed.

[rdsarefun]

I drilled out the passage and tapped this for the screw in jet, believe this is 2.0 mm.  I reads somewhere about machining the portion of idle jet that sticks up into the carb, did nothing with this other than just pressing in.  I do have a new throttle cable on bike that I bought from John, the carb ends have 2 different lengths that can be interchanged. I think I can remove the cable in its entirety and put back together and see if the issue exists or idle drops, and if it goes away, will swap cable ends..  Will jump on it again next weekend, thanks for advice.

[rdsarefun]

I happened to get an hour and pull the carb cables out all together, drop the slides in the bores.  First kick fired up and idled at 1500 rpm.  I bought an new throttle cable when rebuilding and then swapped the ends from the splitter to the carb.  Upon firing it up the rpms increased again.  I noticed the throttle was very loose and the new throttle grip had the handle bar insert where the cable attaches torn loose.  I think this is all throttle cable related, as the adjusters were zeroed out.  Will put on original cable on next week and reach out to supplier whom I purchased the new stuff to resolve.  Bottom line is that it works without the cable.  Thanks all

[rdsarefun]

Another weekend, more time on bike.  I managed to find some NOS cable pieces and put together a factory cable, all sent to my house while I was on the West Coast last week.  Routed cable, reinstalled gas tank and fired first kick with an idle of 1500 rpm's.  No issues turning left to right throttle slides adjusted and I got my first test ride in before the rain started.  Think I am going to get a set of Indian cylinders (that were discussed in another thread)  and do my first port job later this summer after plenty of reading and searches.  Thanks all for the help

[SoCal250]

Routed cable, reinstalled gas tank and fired first kick with an idle of 1500 rpm's.  No issues turning left to right throttle slides adjusted and I got my first test ride in before the rain started.

Congrats on the success

[LMS]

Awesome!    I'm trying to get mine sorted as well, as you can probably tell by all my posts.