Starting Problem

[Foxtee]

Hi All
Fitted twin Mikuni´s to my 750 last week and she fired up on the 2nd try yippie
Went to start on Sunday ( 1st good day we´ve had here for awhile ) fired up 1st time idled for a bit then died , haven´t been able to start since.
Check fuel ...ok, getting to carbs and into engine (wet plugs) ,
No spark ,all wiring mods done some time ago ( before me ) 8.7v @ coils with key on , battery ok holding a good charge.
The 1 thing I think is odd , the neutral & side stand light wink in time with the fuel pump when the key is turned on , I´m suspecting the voltage regulator any ideas

[paso750]

wiring mods done some time ago ( before me ) 8.7v @ coils with key on , battery ok holding a good charge.

this already sounds wrong. With the wiring mod you get the same voltage at the coils the battery has.

G.

[Foxtee]

Thats what I think , so I´ll start at re-doing the wiring to the coils ...... but I´m open to any ideas

[paso750]

what do you mean by it doesn`t start. Does it crank but not fire up or doesn`t it turn over the engine at all ?
If you check electrics thoroughly clean all ground connections.

G.

[Foxtee]

Cranks over no problem , checked -cleaned all the earth points .
There´s no spark when I pulled out the front plug and turned over the engine.
Not sure if when you turn the key on (not turning over the engine ) the neutral & side stand light flicker in time with fuel pump pulsing, if that is normal ?

[paso750]

I guess you would see flicker mainly if battery voltage is low (or if there are voltage drops due to bad connections/wiring)

G.

[Foxtee]

Battery test ok for amps & volts ,so it be a connection some where.
I´ve followed the paso wiring upgrade v2 pdf last nite and re-wired the coils.
I´l crank it over tonite and see what happens

[higgy]

8.7v at the coils is not enough,gotta be a voltage drop in the wiring to the coils or else the starter is drawing too much current...Or a bad battery
I think the first thing I would do is check the wiring for a drop from the coils back to their source voltage. Any drop more than 0.2 volt is an issue
Of course this assumes you know how to do a voltage drop test ?

[Foxtee]

Success
Re wired the 12v to coils as per V2 PDF .....12.2v @ the coils , no more winking lights on the dash fired up 1st time.
Last mod to the coils looked like it was done a few years and worked when I got the bike.
Just need a tune up and a warrant of fitness

[paso750]

good to hear, but although it runs now, be sure to clean all connections if you didn`t do already.

G.

[ducinthebay]

As G. says, clean all connectors on any bike of this age. then coat with silcone grease (dielectric) to keep it fresh. Works wonders.

[higgy]

Actually zinc paste is better(anti sieze),but you first have to take all parts of the connection down to bare metal,wire,terminal,bolt and frame. remove all corrosion.The purpose of any paste or grease is to prevent future oxidation and does nothing to improve the connection. You have to have a good connection first. As a general rule a good connection has a voltage drop of .1 volt or less. Using a good spiked cup washer at all frame contact points is helpful.