complicated carb problem

[gallant_pilot]

Greg you have a point.i have tried to jump start it many times with car battery while the engine was running.
now the only thing might be gone is the CDI,which i will get it tested tomorrow.

tx for advises !

[greg737]

If you have access to somebody who really knows electronics and is good at soldering then your CDI (Ignition Control Box) could be repaired.  The high-amperage induced by the car's alternator will blow capacitors, which is bad of course, but once the capacitors are gone there won't be any further damage to the rest of the CDI (the capacitors are the weakest part and they give up their lives to protect the rest of the CDI).  This leaves you with a situation that can be fixed.

A skilled electrician can identify the blown capacitors and replace them.  This requires a good quality Multi-Meter to identify the bad capacitors (or you can simply replace all of the capacitors), a de-soldering kit to remove the bad capacitors and a precision soldering station to put the replacements in.

Opening up the CDI to get at the circuit board without doing too much damage to the plastic case is a bit of a challenge but it can be done (it's similar to getting into the insides of anything produced by the Apple computer company). 

Here is a link to a very old thread here on the BanditAlley.net forum which was a discussion between members about how to do the capacitor replacement:  http://forums.banditalley.net/index.php?topic=431.0

[Squishy]

Yes it's possible for it to be the CDI but I would always check this last because it's hard to diagnose and can be expensive to replace.
Even still when it has a spark and everything else is good the bike should at least give a sign of life.

[gallant_pilot]

testing it will cost me 5 $ max. also i do have spark.
i am really confused,if everything is fine,why it doesnt fire up.even a single fire would not be unexpected.
i attache a sample picture of timing which i got online and it looks exactly same with my timing.

i removed the spark plugs and put my finger inside the hole and started the engine,i can easily feel the compression which is pretty good and enough for a single fire up.

[Squishy]

That's not how you decided the compression is good right?  Numbers please

[gallant_pilot]

you are right about the compression.its not the right why,but its enough i guess for a single fire.also after replacing the gasket(before skimming the head) i put everything back and it just started easily.but the water was pissing out and i had to get the head and barrels skimmed and lapped the valves.i tested the valves with vacuum tester at engineering and it was fine,also at home i did the liquid test by putting paraffin and was also good and no leakage was seen.then after reassembling it back.i got this problem.

[ventYl]

grg737: wait what? high amperage induced by car alternator? amperage pushed through electrical circuit is direct result of voltage in circuitry and electrical resistance of circuit itself. While resistance is given by circuit construction it's (more or less) constant. Voltage is regulated by regulator to be somewhere between 13,5 - 14,25V. Not different from voltage output of bike alternator. Then current in circuit is given by Ohm's law.

Thus unless car used to crank the bike has faulty regulator or ancient mechanical regulator there's little chance to damage ignitor by using running car to crank the bike. The only difference between car alternator and bike alternator is that voltage output from car alternator drops less with higher current draw than bikes alternator.

If something died from using running car to crank the bike it would die sometimes in nearly future anyways!

But ignitor may be faulty. Capacitors tend to dry out which decreases their capacity and filtering abilities. I have replaced them on one of my ignitors. This may / may not help.

Another problematic part of original ignitors are final stage high-gain bi-polar transistors which do all the rough work and pass quite a huge currents through ignition coils. These tend to raise their resistance over time which causes to generate more heat and in turn raise the resistance even more until engine stops to work. This causes smaller voltage/current to be applied to ignition coils and thus weaker spark.

Even if spark is present when plug is out of engine it may not be able to crank. Even with brand new plugs. I experienced this once when the only action which helped was to replace the final stage transistors with new ones.

Bad news is that current electronics is using unipolar transistors for high-current switching circuitry so there are no transistors available offering switching capabilities of original parts nowadays. IIRC original transistor had h21e (gain coefficient) of over 500. Current transistors which are available have h21e coefficient at best of 1/3rd of original. In my ignitor darlington-type TIP150 from fairchild worked well and provided enough gain to create spark which is able to run the engine (not only spark out of engine). It is also mechanically and electrically compatible so you do not need to adjust PCB/circuitry or change position of anything inside. Just desolder old and solder new.

If final stage transistors need to be replaced can be examined by connecting terminals to oscilloscope and read voltage between ignitor terminal connected to coil and ground during the phase when transistors are open. Ideally it would be 0 but as the transistors are old they build some resistance which in series with quite a low resistance of ignition coils causes voltage buildup on transistor. I cannot provide figures of what voltage is already bad and which is good but if voltage is different for left / right coil and / or if it is larger than 1V I would replace final stage transistors for new ones.

[greg737]

See how that happened, works every time...

It's a little-known fact that there are highly-qualified electrical engineers walking among us all the time.  They normally refuse to offer electrical help or advice until, that is, somebody who doesn't know much about the science of electronics says something that doesn't quite make sense.  And that person is ME.

You're welcome.
 

So, apparently the "don't jump-start a motorcycle from a running car" is an absolute myth.

This is actually very interesting to me because it begs the question: Why is this caution/warning about doing damage to the motorcycle's electrical system so widespread?

I'd hazard a guess that this erroneous caution/warning to the unwashed masses (of electricity-ignorant riders) grew up out of the more basic danger of damage that will result from something like accidentally hooking up the jumper cables to the wrong polarity on the battery. 

[gallant_pilot]

Yes it's possible for it to be the CDI but I would always check this last because it's hard to diagnose and can be expensive to replace.
Even still when it has a spark and everything else is good the bike should at least give a sign of life.

i finally got the CDI tested today and they said its faulty.however i didnt believe them as they are bunch of screwed ppl,so i took it to aeronautical electronic guys and asked them to have a look on it.


i did the compression test myself today,however it was headache to find adapter for it.anyways,i did some dry and wet test.my GOD it was nothing not even 100 Kpa.then i added some oil and cranked it for few second and it went up to 700 on one and the others 450 and 500 more or less.

with regards to what i have done on the head and valves plus the new aluminum gasket i put,it should be the rings or pistons,however i checked the barrels and they were fine and smooth and free of any single scratch, also my mechanic said that the pistons and rings look  fine.

now whats next?

[Squishy]

Told ya, do a proper compression check.
Yes it does sound like piston rings but for them to be 100kpa they almost have to be missing or you have a hole cylinder walls.

You did have the throttle wide open during the test, right?

[gallant_pilot]

it might sound funny,but honestly it was my first time to check the compression.the dry test,i just cranked the engine for like 3 seconds and didnt hold the throttle open.but after adding oil i did open it and cranked it for longer.the readings are as below:

from the left

1- +- 650
2- +- 250
3- +- 400
4- +- 350

now how can i do the dry test again while the oil is still there and what do the numbers have to say?

[Squishy]

The oil will drain down and get into the oil pan. That's ok.
Hold the throttle open and crank the engine.
It should be >800kpa on all 4 and between them not more than 200kpa diffierence.

[gallant_pilot]

well,i am gonna leave the bike for while and the oil probably will drain out into the sump.i will try it again and see what it reads.

is there any way that we can catch up on whatsapp.viber or maybe imessage?

if yes,plz add me and text me there as it would be quicker sometimes than the forum!.
+27837667118

[ventYl]

greg373: for same reason why constant voltage-type chargers have usually capacity rating in form from-to and/or switch for bike/car (by which I don't mean switch 6V/12V which is separate): car alternator can deliver quite a good portion of amperes until output voltage starts to drop. let's say 40 amperes when idling. If you are cranking your bike using external power source there's strong assumption that your battery is discharged. Fully discharged battery has quite a low resistance so you can easily apply so much current to charge the battery that it will boil, electrodes will bend or any sort of different bad thing (TM) can happen.

edit: while people are dumb enough to dry their pets in microwave oven they may be dumb enough to crank/charge their fully discharged batteries (in fact it is not needed to be much dumb to do that) by running car and boil them.

Bike generator has less power so even if by some miracle you manage to crank it up with completely dead battery, voltage drop would be so huge that ignition stops working. And even if not it won't have enough power to fry your battery.

BUT with fried battery there's no voltage stabilizer in circuit and running bike without bat you can damage both generator and ignitor.

If you are cranking the bike with running car connected and with bat at least slightly charged it will have higher resistance and chances to charge it too fast are smaller. But by no means this could directly damage ignitor itself.

Bandit's ignitor is simply not much reliable. Youngest one is more than 15 years old. Most of ignitors "on the road" are 20+ years old. Electrolytic capacitors contain fluid which creates their capacity. They are long and heavy compared to their electrode dimension so they are sensitive to vibrations even despite the fact they are glued inside ignitor by flexible glue. They are also sensitive to heat. Heat and vibrations are two factors which are present in huge amount on bike. So capacitors tend to die during the years. But more heat-sensitive parts are final stage transistors. On both mine Bandits ingitors were dead. One was repaired by myself (first: final stage transistors were replaced as described above which brang the ignitor back to life then: replaced capacitors to avoid need to disassemble it once again). Another bike has it's ignitor replaced for several years. First bike was cranked for several tens of minutes after ignitor was re-mounted after repair using running car with no damage at all. Battery has lower capacity but it is already quite old and was sitting discharged for maybe one year so it was considered as already dead.

[gallant_pilot]

after almost 24 hrs, i did another set of compression test!

i think the time was enough for all the oil inside the barrels to settle down.

         dry test                         wet test
4-          250                              200

3-          450                              450

2-          200                              250

1-          550                              550

my guess is that the rings are still good.
but now what else can cause this low compression?

1-head gasket is aluminum freshly cut
2- head bolts are tighten 25 n/m
3-valves have been lapped and valve seats are cut
4- timing is as manual
5-barrels are free of any scratches.