If I have the HRC center mount cylinder kit, can I use a regular long plug on the top cylinder and a short plug on the bottom cylinder?

I use regular plugs on both ... wouyld be interested to hear if I shouldn't be, or at least what the other options are.
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ripready wrote:If I have the HRC center mount cylinder kit, can I use a regular long plug on the top cylinder and a short plug on the bottom cylinder?

Yes. That's how mine is set up. May be an idea to try and get a 9.5 short plug if you can (I don't think NGK do a 9 in the short plug).

It's not really a problem using the standard BR9ECM with the HRC setup, only that it fouls the bodywork.

Be careful if you pull the forks up through the triple clamps though, as you may then run the risk of tyre to spark plug contact.

It is an idea to use the standard plug in the lower cylinder to do your initial plug chop(s) as they are easier to read than the RS plug, as Wrench mentioned in a recent post.
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Actually I was thinking about buying the VHM heads from Jha. They run the RS type plug on both. I figure I would be cheap and run only one as those RS plugs are expensive.

The recommendation from Jha is to use the short plugs on both but they emphasized using the short plug on the lower cylinder as the front wheel can hit the spark plug under heavy load.

I can't see any reason why I can't run two different plugs as long as they are the same heat range. However, I save like $50USD on not using one for the top cylinder.

I really don't get this thing about the spark plugs hitting the front wheel business. I've got the HRC head mod going on, and the normal plugs. My spark plug cap is just nowhere near the fron t wheel . Furthermore I have got an RS250 front end which drops the front way down and brings it closer than it wouuld be ... and at the track I've been bottoming out so that the front fender is hitting the upper fairing. And still the front wheel is nowhere near the plug.
In fact the HRC water hose sticks out further than the plug does anyway ...
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MC28 SE -sold-
MC21 with RS250 engine -for sale-
MC21 race bike -soon for sale-

Really?

Before I had my forks rebuilt, I used to grind the plug cap off under hairpin braking. Used to get through a cap per weekend meet - and that's with a normal front head!

Maybe you have the chopper front end conversion?
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Yep same here ground away cap at the hairpin that was with the conversion.No probs with the short plugs,apart from the large hole in my pocket!.

Dave Ett wrote:Really?
Maybe you have the chopper front end conversion?

Quite the opposite, I've got the extreme-rake RS250 front end conversion. This is too strange. I've got a race fairing, and I had to cut out the front a little where the plug sticks out, but it doesn't really protrude beyond the fairing. I'm going to go and take some pictures, I can't see how it can be soooo different for us!
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MC28 SE -sold-
MC21 with RS250 engine -for sale-
MC21 race bike -soon for sale-

I have the same setup. RS front end, stock plugs, head conversion. With the stock bodywork, I had to trim the plastic a little, but the plug still does not protrude past the plastic. And I never have a problem with the tire getting anywhere near hitting the plastic.

VHM heads would be a different story, though. Those heads have the plugs dead center and sticking straight out the top, not angled like the NSR top head. You may have some clearance issues there.
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Paul Herr
'88 FZR4/GSXR/YZF Frankenbike
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