Running great until.....lots of questions

[78rd420]

Hello all so got a 78 400c stock carbs,air box,mild porting,DG pipes Twoomey silencers,brother bought new i restored in 2005.Fast forward 2015 bike been sitting few years put new gas plugs has injector oil fires right up buzz the neighborhood runs ok next day go for ride about 2-3 miles she slows down and quits starts up but shitty tear it apart left side seized suspect major air leak main seals? manifolds ok,injector lines clogged?Will investigate and fix.So its time for major upgrade so my thoughts after reading many posts and respect them all WHAT is best for my application??1.IGNITIONS:Seeing prices from $300-600 looking for affordable,dependable,no haasle haha set up. 2.CARBS:many discussions flat,round,28-34 sizes.My deal is would like to use stock cable and throttle assy with injection so i have a set vm 30s need rebuilt or buy new so will any carbs work with stock throttle assy?Would rather do new pwk28s?REEDS:Wich ones v force,yz,use what i got?(see pics).Just looking for a little bit more i know it can run better with these upgrades and any other suggestions Thanks Scott

[Czakky]

That is not a half ass seizure, eh?

[Evans Ward]

That is not a half ass seizure, eh?

Sure looks like it.

[~JM~]

Have the heads modified for today's lower octane pump gas.

[Yamaha 179]

That's a very nice bike.  I'd recommend you find the reason for the problem, probably a leaking crank seal, fix that and think about rebuilding the crank too.  You should contact contact Chuck Q about boring the cylinders and ask him about the porting at that time.  You said it is mild; mild porting with pipes is a pretty good street combination and it's been a while since you've had it and maybe it
will be just right for you.  You don't need big carbs and the stock ignition system works well if you don't mind cleaning and setting the
points twice a year (depending how many miles you put on it), and you can always add the iggy later.
Lyn Garland

[m in sc]

^ this. get your baseline sorted first. 

[SUPERTUNE]

Scott,
These RD's just need some special guidance to be reliable on pump gas, this is not the 70's and 80's when we could get away with a lot of stuff we did to them.
Just need to go through the entire setup.
Depending on how big the bore is, stock heads are good to 65mm. I would cut them for reduced cc's after 65.25. this is on stock or mild porting setups.

One big role is to have a rebuilt crank or at least inspected, trued maybe some new outer main bearing with new seals at minimum.
That's your foundation to start, then fresh bores and pistons, then setup proper intake system and carbs to suit.
I like to drop the front sprocket a tooth for RD with chambers to lesson the detonation load on the engine with todays pump fuels. 16/38
Start with 1.9mm BTDC ignition timing. If on a stock coil system you will want to do a coil relay mod to keep the spark strong to handle rich jetting to live on pump gas.
Vintage Smoke Ignition is a points replacement ignition and is great for just that, you must have the rest of the stock charging system
healthy and working. The Vape (powerdynomo) CDI is a modern system and replaces all of the charging system as well. much better in the long run, but more expensive and more work for the first install. (see my posts about installing them in the vendor section)
Try and look on ebay for new oem Yamaha points (for the 1A1 model not 2V0) if needing to stay on them for now, aftermarket points can be hit or miss a lot of the time.

The 30's you have will work great rejetted, if you machine them to fit your manifolds (or buy new manifolds) and with just some minor cable work,you can keep your stock throttle setup with the oil pump once you do a rebuild and test on it.
Need to find some reed stops and trash those Boyesen 2 stg reeds, good on a stock bike only, but too restrictive in upper rpm's and will help keep you in trouble and you have too much of that now...
Use some OEM Yamaha YZ125 reeds or some TDR's with modded stock cages. Get a stock Banshee crossover or go all out with one of my TSR/Barlow designed boost bottles, do not use a Banshee aftermarket boost bottle.

Send me an email and we can talk if you need help.

Chuck