• Required reading for all forum users!!!

    Welcome!
    Register to access the full functionality of the GSResources forum. Until you register and activate your account you will not have full forum access, nor will you be able to post or reply to messages.

    A note to new registrants...
    All new forum registrations must be activated via email before you have full access to the forum.

    A Special Note about Email accounts!
    DO NOT SIGN UP USING hotmail, outlook, gmx, sbcglobal, att, bellsouth or email.com. They delete our forum signup emails.

    A note to old forum members...
    I receive numerous requests from people who can no longer log in because their accounts were deleted. As mentioned in the forum FAQ, user accounts are deleted if you haven't logged in for the past 6 months. If you can't log in, then create a new forum account. If you don't get an error message, then check your email account for an activation message. If you get a message stating that the email address is already in use, then your account still exists so follow the instructions in the forum FAQ for resetting your password.

    Have you forgotten your password or have a new email address? Then read the forum FAQ for details on how to reset it.

    Any email requests for "can't log in anymore" problems or "lost my password" problems will be deleted. Read the forum FAQ and follow the instructions there - that's what we have one for...

  • Returning Visitors

    If you are a returning visitor who never received your confirmation email, then odds are your email provider is blockinig emails from our server. The only thing that can be done to get around this is you will have to try creating another forum account using an email address from another domain.

    If you are a returning visitor to the forum and can't log in using your old forum name and password but used to be able to then chances are your account is deleted. Purges of the databases are done regularly. You will have to create a new forum account and you should be all set.

Dunstall GS750 eating spark plugs

  • Thread starter Thread starter jock
  • Start date Start date
J

jock

Guest
Hi there - I have a problem with my 1981 Dunstall GS750. It runs dyna ignition, Accel coils and HT leads and gets through NGK B8ES (also tried BR8ES) plugs at a fair old rate. The problem starts with the engine running on 3 or less cylinders and its always an arcing or weak spark plug to blame, fitting new standard plugs always cures it and it runs like a good un for a while. The engine was tuned from new at the Dunstall factory and is fitted with 29mm Mikunis from VBS (Pip Highams tuning shop in Manchester) and higher compression ratio. It goes like stink when its sparking properly.

Is it possible that the standard plugs aren't up to the tuned ignition / engine ? Can you recommend a higher rated plug that will work better ??

Thanks in advance for your help

Cheers
 
Hi Jock. Is every thing set up right: ignition timing, valve timing, carb settings (plug colour) etc.

And what do the plugs look like? Are they burned away etc?

Oh - and are the valve clearances OK? They can throw things.
 
I think spark plugs are merely a symptom of something else which is likely wrong

1) Dyna Coils? Do they have the correct resistance . . . Verify by measuring with a DMM ( I believe 3 Ohm is correct)
2) Any mods done to the wiring harness leading to the coils . . . Ballast resistor or some other mod
3) HT Leads? Swap existing wires with another set . . . problem perist?

Cheers
 
Last edited:
srsupertrap said:
I think spark plugs are merely a symptom of something else which is likely wrong

1) Dyna Coils? Do they have the correct resistance . . . Verify by measuring with a DMM ( I believe 3 Ohm is correct)
2) Any mods done to the wiring harness leading to the coils . . . Ballast resistor or some other mod
3) HT Leads? Swap existing wires with another set . . . problem perist?

Cheers
Click to expand...
How about high compression and low octane gas!
 
Forget the plugs .
I'm chasing a pitcha of yer bike .
A Dunstall GS has got to be very unique .

Cheers , Simon . :)
 
Dunstall GS750

Dunstall GS750

Thanks to everyone for the advice. To answer a few of the questions - the valve shims are all in tolerance, the faulty plug always looks normal and isn't burned away at all, the carbs run k&N pods and are balanced (it ticks over at 1000 perfectly). I will check on the other points like coil leads and the Dyna settings over the weekend and report back.:)

I have created an album to try and show you guys some pictures of the bike but it wont allow uploads - just keeps saying "upload failed". I have contacted the administator to try and figure it out.:confused:
Its a beauty in its Heron colours and pretty rare - I dont think Dunstall made many GS750s cos the Dunstall GS1000CS came in and stole its thunder. I,ve seen a few Dunstall GT750 Kettles about but no other GS750s.
 
If she's all on pat then it's probably worth putting some colder plugs in there - NGK B9ES or Champion N2 - and see what happens. If she starts fouling plugs then that's not the answer.
 
Which plug is it? I would switch the plug leads with it's mate (1-4, or 2-3) and see if the problem follows the plug lead. If so, then that wire is bad. I have also seen wires arcing to the frame, so rule that out too. One other possibility would be a twisted crank, if 1 or 4 is the problem.
 
A test you can do is when a plug is not sparking hold it about an 1/8th" off the cylinder head and see if the spark jumps from the plug body to the head. If it does then get back to us with the results.
 
Start with the basics

12V or better power to the coils?

Swap leads as suggested

Do you have the HT leads with yellow wires/red boots? One of mine fried itself at the boot, had to pull the boot and cut the wire back to a clean surface, 30 years of arcing there can play hell with that crimp fitting
 
Here's a photo of a Dunstall Kettle I found.

suzuki-dunstall-gt750.jpg


And a GS750.

78suz.jpg
 
Thanks to everyone for the input - I'll put in some garage time at the weekend and report back (I'm fitting spoked wheels at the same time cos I think they look better than the alloys - just had them rebuilt with stainless rims and spokes). Still can't upload photos :confused:
 
jock said:
Thanks to everyone for the input - I'll put in some garage time at the weekend and report back (I'm fitting spoked wheels at the same time cos I think they look better than the alloys - just had them rebuilt with stainless rims and spokes). Still can't upload photos :confused:
Click to expand...

Keep your garage locked Jock. Although I'm a long way south I'm still tempted to come up and pinch those wheels..... You can't beat a GS with spoked wheels.
 
dunstall plug problem update

dunstall plug problem update

Just a quick note to update everyone on this problem - after much investigation and the help of an auto electrician it turned out to be a faulty coil lead. Bikes running great now and looking forward to summer !!

Thanks for help everyone.

Cheers !
 
You must log in or register to reply here.

Similar threads

KiwiAlfa156
Retarding Ignition Timing
2
Replies
25
Views
589
rphillips
R
sam000lee
Post GS750 > 844 Build Plug Fowling
Replies
10
Views
254
rphillips
R
Tashields21
New Coils, no spark at 1 and 4. Narrowed down to CDI (maybe?)
2
Replies
33
Views
721
gs scott
gs scott
martin_montreal
1978 GS750 Head, 4:1 exhaust, spoked wheel, some background & advice
Replies
6
Views
276
kochic
kochic
A
GS750 No spark/Starter no longer working
Replies
4
Views
249
alkswheetinjur
A
Back
Top