Bike won’t start. I found the problem.

[MikeyVeitch]

Bandit 6 frame but with 1127 gsxr everything (coils plugs engine carbs harness cooler clutch switchgear exhaust)

I found the problem with my bike not starting… but how do I fix it?

If I hold a spark plug in the ht lead, it arks to the frame. I know it’s a strong spark because because one, it’s fucking big. Two, it’s fucking blue and three, it’s arking a good 2cm. 
All seems well. 
When I actually ground the spark plug body against the frame. No ark. If I hold it against the engine. No ark. The coils are connected correctly as per the wiring diagram. Even then, I’ve tried the wires every way around. Any reasons as to why the spark plugs would behave in this way?

[TonyGee]

have you tried brand new plugs ? 

[MikeyVeitch]

Yes. Everything to do with electrical on the bike has been replaced. Plugs coils caps stator/pulse generator. 
Waiting on a new harness to try but I think it will make fuck all difference 

[bluedog59]

Have you had the frame/engine painted ? Try running an earth strap from engine to frame making sure you get a good earth to bare metal.

[MikeyVeitch]

Both have been sprayed but the ground areas have been cleaned. Both are grounded direct to the battery with nee cables. 

[DAZ]

Have you still got the old plugs ,or someone with the correct plugs in a running bike you could try swapping plugs with, just chucking an idea that maybe the new plugs are faulty in some way..did you get them from a reputable source as there has been counterfeit products on Eblag before now

Edited March 18, 2023 by DAZ
Addition

[MikeyVeitch]

Got 2 new sets, one old set and a working set from a katana. None work on this

[Captain Chaos]

2 hours ago, MikeyVeitch said:

Everything to do with electrical on the bike has been replaced. Plugs coils caps stator/pulse generator. 

what about the CDI unit?

[DAZ]

15 hours ago, MikeyVeitch said:

Bandit 6 frame but with 1127 gsxr everything (coils plugs engine carbs harness cooler clutch switchgear exhaust)

I found the problem with my bike not starting… but how do I fix it?

If I hold a spark plug in the ht lead, it arks to the frame. I know it’s a strong spark because because one, it’s fucking big. Two, it’s fucking blue and three, it’s arking a good 2cm. 
All seems well. 
When I actually ground the spark plug body against the frame. No ark. If I hold it against the engine. No ark. The coils are connected correctly as per the wiring diagram. Even then, I’ve tried the wires every way around. Any reasons as to why the spark plugs would behave in this way?

If it is arcing from the tip of the plug  to the frame and not to the earth strap on the plug or any part of the plug body surely it is the plugs? Does it are from the body of the plug to the engine or frame if not in contact ? Maybe the insulation between the core and body is defective, you've tried the other plugs you have IN this bike not just arcing to the head, just double checking.

 

[imago]

It sounds like the current is jumping/running through to the plug body before the tip, which would be either the plugs or the leads.

When the plug's out the current flows into the plug body and jumps to the earth path (head or frame). When the plug's in the head there's no gap to jump because the current flows directly from the plug body to the head via the threaded connection.

On the image below you can see what I mean. At the very bottom it should jump from the red electrode to the 'hook'. If it arcs or connects before that then it makes a circuit and won't jump. Electricity like water will always take the path of least resistance.

 

[Dezza]

I had a similar problem a few years back and it was a faulty CDI unit.

[imago]

19 minutes ago, Dezza said:

I had a similar problem a few years back and it was a faulty CDI unit.

Usually a CDI issue will either cause the spark to fail when it's in a cylinder under compression because it's weak, or it doesn't fire at all on one coil.

 

Edited March 18, 2023 by imago

[MikeyVeitch]

27 minutes ago, imago said:

Usually a CDI issue will either cause the spark to fail when it's in a cylinder under compression because it's weak, or it doesn't fire at all on one coil.

 

Tried 3 cdis. One is from this bike, one  that I had spare and the last being from another healthy running bike. 
 

[MikeyVeitch]

UPDATE:

I think I’m starting to narrow down the problem. 
when the bike was running, it had a mismatch of plugs. I tried one of the old plugs and whatever cylinder I put it in, it works. The old plugs is an NGK DPR8EA-9 and the new ones I’m trying are JR9B. I’ve just put another set of the new ones in and the same happened again. It runs on all 4 for a couple minutes and they drop off one at a time until the bike no longer goes bang at all. Do you think that I would try a new set of the DPRs?

[DAZ]

Jr9b is std gsxr plug so should work ,but now they run for a couple of minutes before dying off ? What coils are you using, do they get over hot? 

[TonyGee]

48 minutes ago, MikeyVeitch said:

UPDATE:

I think I’m starting to narrow down the problem. 
when the bike was running, it had a mismatch of plugs. I tried one of the old plugs and whatever cylinder I put it in, it works. The old plugs is an NGK DPR8EA-9 and the new ones I’m trying are JR9B. I’ve just put another set of the new ones in and the same happened again. It runs on all 4 for a couple minutes and they drop off one at a time until the bike no longer goes bang at all. Do you think that I would try a new set of the DPRs?

whats the condition of the plugs after it stops running, are they wet/sooty or dry ?  could be a fuel problem !!!  

[Dezza]

Try Nippon Denso plugs. The NGKs may be knock offs, especially if sourced online.

Edited March 19, 2023 by Dezza

[MikeyVeitch]

2 hours ago, TonyGee said:

whats the condition of the plugs after it stops running, are they wet/sooty or dry ?  could be a fuel problem !!!  

Defo spark mate. I am using b12 mk1 carbs and a kat750 with the same carbs. Swapped the carbs over and the katana still rand and the 1100 still doesn’t. I have crossed everything between the two bikes apart from the harness and the plugs because they are different. The katana never stopped running and the 1100 never started meaning of I’ve ruled it down to those two things

[MikeyVeitch]

2 hours ago, DAZ said:

Jr9b is std gsxr plug so should work ,but now they run for a couple of minutes before dying off ? What coils are you using, do they get over hot? 

I’ve used original ones off the bike, bandit 1200 ones, kat750 ones and got some brand new genuine Suzuki ones. Still no start

[TonyGee]

not something that give much trouble but could it be the pulse coils ?  or maybe its a wiring fault ? 

[MikeyVeitch]

1 hour ago, TonyGee said:

not something that give much trouble but could it be the pulse coils ?  or maybe its a wiring fault ? 

Same as the other stuff pal. Tried the one off the katana750. Was a cunt to change over but still made no difference 

[TonyGee]

18 minutes ago, MikeyVeitch said:

Same as the other stuff pal. Tried the one off the katana750. Was a cunt to change over but still made no difference 

other than the harness its got me !!!!  

[bluedog59]

The issue to work out now is whether it stops running due to.

A. Power failure to the plugs .

B. It's killing the plugs.

C. Fuel supply.

Just because the carbs worked on another engine, don't assume anything.  Check all the fuel lines, breathers etc including the tap and tank vent.

[george 1100]

I had a problem similar to this with NGKs and the thing is, you assume they're working 100% because they're new, so you set off on a goose chase, driving yourself insane until you come full circle and realise the new plugs you put in were no good

Edited March 19, 2023 by george 1100

[Dezza]

Looks like Denso are being faked too

https://www.denso-am.eu/news/deneur19_33_counterfeits

 

Edited March 19, 2023 by Dezza