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Kawasaki GPZ 500S 1988
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Discussion Starter · #1 ·
Hey,

So my flywheel threw it's magnets a while back. I replaced it with a gen2 one (doing the mod to fit it to my -88). Also replaced the CCT.

But my bike still refused to start, so I bought new spark plugs, installed them and cleaned out the caps. I tested for spark and both sides have spark.

Also tested to battery voltage when cranking, and it read about 11V and then dropped to 10.8 after a bit.

The bike will sometimes do a few "brut brut"' sounds, but won't start up. Any ideas?
 

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07 Ducati SS800 '95 Ducati 900SS/SP '19 Honda CBR650R
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you've verified fuel actually flowing to carb bowls? Exactly how long is "a while back" ? Last valve clearance check how many miles ago?
 

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as above, and that battery isn't strong enough anything below 11v while cranking will not start the bike.
 

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Discussion Starter · #7 ·
Update;

Carbs had fuel in them. The battery should be fine. It was starting the bike fine before the flywheel broke, and has been charged often.

I'm pretty sure I did the mod correct. I measured the distance on the old flywheel and took that off the new one. Measurements were similar to the ones FOG provided in the guide.
 

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So if everything is correct it should be starting yes, only it isn't. there is an old saying "if your bike was running fine before you did something and now it won't go there is a 99% possibility whatever it was you did is causing the issue". given the trigger strip cut is correctly, (I assume you checked both flywheels side by side) it must be something else.

personally I think your battery voltages are too low, mine have been stood a few weeks but the battery voltages (ignition on) are in the 12.75v range and the starting voltage in the 3 seconds or so it takes them to fire up never drops below 12v.
 

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so the fuel is a "few" months old? Purge/remove it in favor of fresh.
i'd never trust the word of the PO. I'd suggest doing a check....what 2-3 hours total (?) and easily worth knowing they are in spec after correcting them (if needed)
reiterating my .02...nothing further to add.
 

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Discussion Starter · #11 · (Edited)
Hey, just did valve check, put in new fuel, new coolant. Tried to start, but got this. Anyone know what could be making that sound.


Should mention, the "speed up" was from me adding some gas.
 

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Anyone know what could be making that sound.
yeah it's not firing, just compression restricting the engine from turning over. quite normal. until it fires (yours isn't) you sure the trigger strip is bang on, if it was cut a few mm short it would do that as the timing would be retarded.
use the formula 1mm = 2 degrees of advance/retard are you sure the plugs are firing under compression.
have you got a tester or one of those old fashioned strobe ignition lights.
 

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Discussion Starter · #13 ·
yeah it's not firing, just compression restricting the engine from turning over. quite normal. until it fires (yours isn't) you sure the trigger strip is bang on, if it was cut a few mm short it would do that as the timing would be retarded.
use the formula 1mm = 2 degrees of advance/retard are you sure the plugs are firing under compression.
have you got a tester or one of those old fashioned strobe ignition lights.
Did the cut according to FOG instructions.

Could you explain this "1mm = 2 degrees of advance/retard" ? Never heard of it
 

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Fast Old Guy
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he means 1 mm .03937 "of displacement of the trigger strip on the periphery of the flywheel will alter the ignition timing 2 degrees of crankshaft rotation.
this amount will not prevent starting though , but will affect performance .
You must be sure you have the new flywheel altered the same as the old one in relation to the woodruff key slot.

FOG
 

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Did the cut according to FOG instructions.

Could you explain this "1mm = 2 degrees of advance/retard" ? Never heard of it
no you wouldn't have it's not written down anywhere. fog is correct however if the "cut" is wrong by a few mm or in other words "short" it would make the timing retarded.
basically the flywheel rotor is a circle so has 360 degrees at any point on the outside rim. the outside diameter is as near as dam it 720mm (16in) so for every 1mm of strip it equals 2 degrees of timing.
 

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Discussion Starter · #17 ·
are you sure the plugs are firing under compression.
have you got a tester or one of those old fashioned strobe ignition lights.
I don't have a tester. Is there any other way for me to tell? I had pretty decent spark in room pressure when I checked it
 

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Discussion Starter · #18 ·
he means 1 mm .03937 "of displacement of the trigger strip on the periphery of the flywheel will alter the ignition timing 2 degrees of crankshaft rotation.
this amount will not prevent starting though , but will affect performance .
You must be sure you have the new flywheel altered the same as the old one in relation to the woodruff key slot.

FOG
Actually, sorry. I re-read the guide and want to ask for some clarification. Are you supposed to cut off all the other material as well, in addition to taking some material off the "actual" trigger strip?
 

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That can't be right. 720mm is almost 2 & 1/2 feet.
good catch. that's what you get trying to think @ 4am after just finishing a 10hr poker tournament. quite right it's true circumference is 16in you can do the maths yourself, principal is just the same. 1mm = 2degrees of timing.
Actually, sorry. I re-read the guide and want to ask for some clarification. Are you supposed to cut off all the other material as well, in addition to taking some material off the "actual" trigger strip?
yes. when you have finished the modified flywheel should look exactly like the old gen 1, with just the one 30mm trigger in place on the outside everything else on the outside must be removed including the small one on the other side.
edit, just for reference the distance between the start of the strip and the "T" mark is 59.40mm.
I don't have a tester. Is there any other way for me to tell? I had pretty decent spark in room pressure when I checked it
No not really, people forget these bikes are old technology (80's) so sometimes the old type tools are the best to have for diagnosis purposes.
 
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