carse
|
| posted on 19/4/16 at 08:11 AM |
|
|
Spark plug damage causing a misfire under load?
Hi all,
Hoping for a little help/advice from someone more knowledgable than me on an issue I'm having with the motor in my Indy R.
I built a new GSXR 1000 K4 engine for it (cams, head work, high comp gasket, remap - nothing super serious or expensive) and when putting it back
together I, er, managed to overlook putting in the four rubber o-rings that seal the cam cover to the head around the PAIR air bleed/emissions valves
in the head.
The motor ran, but it was obviously sucking in a lot of oil in the process as it was escaping into the chambers through the PAIR valve. Having fixed
this issue by putting the o-rings back in, it now runs fine at idle, but under load (seems to happen around 6,000rpm quite regularly) the engine
starts to misfire quite badly - almost like a pit lane limiter.
I've checked the fuel pump and filter - they're both fine. The injectors are also clean and I'm pretty sure there's not a
fault in the loom.
So, my suspicions lead me towards the oil that was being burnt initially fogging/gunking up the spark plugs on a microscopic level, which affects the
spark under load at a certain point?
Anybody got any thoughts as to whether this could be a reasonable diagnosis?
I'm not with the car at the moment, but will be chucking some new plugs in it to test on the bank holiday weekend.
Was wondering if anyone had heard of/experienced anything similar on a bike engine?
Cheers,
Sean
http://www.pistonheads.com/doc.asp?c=52&i=28450
|
|
|
|
|
Oddified
|
| posted on 19/4/16 at 08:24 AM |
|
|
It may be the plugs, but it could also be that the ignition system isn't up to firing the plug/fuel under load (leads/coils etc due to the extra
compression and load). Quick and easy way to check for the latter is reduce the plug gaps slightly and re-test, the smaller gap is easier for the
spark to jump under load and pressure.
Ian
|
|
|
carse
|
| posted on 19/4/16 at 08:57 AM |
|
|
Thanks for the reply Ian. Good point as well. I'm hoping it's just the plugs (maybe in vain) as the cams and gasket are a fairly widely
adopted mod in bikes, especially in the US. I will try what you say - and new plugs - and see if it makes a difference.
Here's hoping.
Sean
http://www.pistonheads.com/doc.asp?c=52&i=28450
|
|
|
adithorp
|
| posted on 19/4/16 at 09:25 AM |
|
|
Plugs in bike engines are notorious for not recovering after being wet/contaminated.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
|
|
|
carse
|
| posted on 19/4/16 at 09:41 AM |
|
|
Adithorp, thanks for the reply. Good to know.
Cheers,
Sean
http://www.pistonheads.com/doc.asp?c=52&i=28450
|
|
|
motorcycle_mayhem
|
| posted on 19/4/16 at 10:44 AM |
|
|
Again, plugs are very sensitive in bike engines.
They may be visually great, but they'll still cause so many issues, the one you describe is common.
Having said that, the GSXR's have been better in tolerating plug imperfection (in my hands) than most. Least tolerant have been the R1
ignition-stick family, all it takes is to start the engine cold, let it run for a few minutes and then shut it down. It will then miss, or (more often
than not) see one pot totally inactive, until a change of plugs.
|
|
|
carse
|
| posted on 19/4/16 at 11:43 AM |
|
|
Thanks m_m.
From memory, they're not even visually great. No signs of obvious damage, but electrodes are very dark with a black, soot-like coating showing
it's been running rich due to the oil - not the light brown/tan colour you'd expect from a motor with a decent fuel map in it (the plugs
came out of a standard K4 unit with a bespoke map in and were fine when they went in).
Didn't initially cross my mind that this could have been the issue, so hoping new plugs will fix it.
Cheers,
Sean
http://www.pistonheads.com/doc.asp?c=52&i=28450
|
|
|
adithorp
|
| posted on 19/4/16 at 02:51 PM |
|
|
quote:
Originally posted by motorcycle_mayhem
...Least tolerant have been the R1 ignition-stick family, all it takes is to start the engine cold, let it run for a few minutes and then shut it
down. It will then miss, or (more often than not) see one pot totally inactive, until a change of plugs.
Oddly never had an issue with mine as far as I can remember.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
|
|
|
russbost
|
| posted on 19/4/16 at 06:18 PM |
|
|
I would also add fuel to the fire re bike plugs, I have found that once fouled, for whatever reason, it's almost impossible to get them to work
properly again. From experience with old ZX10's & new ZZR1400's, despite the many differences in old & new engines had the same
issues with plugs on both. New plugs fitted fixed everything!
I no longer run Furore Products or Furore Cars Ltd, but would still highly recommend them for Acewell dashes, projector headlights, dominator
headlights, indicators, mirrors etc, best prices in the UK! Take a look at http://www.furoreproducts.co.uk/ or find more parts on Ebay, user names
furoreltd & furoreproducts, discounts available for LCB users.
Don't forget Stainless Steel Braided brake hoses, made to your exact requirements in any of around 16 colours.
http://shop.ebay.co.uk/furoreproducts/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
|
NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
|
