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TOPIC: Never Mind Air Injection, What About a PCV System?

Never Mind Air Injection, What About a PCV System? 1 week 5 days ago #27858

  • rdurost
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My US-spec '82 has the passive air injection system, which is not required in my very rural area. There are probably less than 25 bikes in the entire county. There are only three towns, with a total population of under 1500. Air pollution, apart from the annual wildland fires, is in no way an issue.

Anyway, while I will be removing the air injection system for the sake of simplicity and weight, I know that there is no downside to a Positive Crankcase Ventilation system. It allows blow-by gasses in the crankcase to be burned rather than vented to the atmosphere, which has no effect on performance and furthermore, makes the engine last longer by extracting highly corrosive gasses from the crankcase.

So. What I want to do is replace the AIR system with a PCV system. There is already a crankcase vent that was connected to the air box at the factory. I no longer have an air box, but I will have an oiled-gauze filter (like a K&N) on that vent, so all I require is to have another source of vacuum to pull in the gasses from the crankcase through the filter at the vent.

There are countless generic PCV valves on the automotive market, including many that come with a large selection of airflow-restriction "washers" to keep them from becoming an excessive vacuum leak, while preventing backfires from igniting the blow-by gasses. So I guess my question is, what is a good source of vacuum other than the three vacuum taps on the intake manifold? I want to keep those clear for other applications. I suppose I could drill and tap the three "plenums" but really this is an IR carb system, and I'd rather do nothing to disturb that.

I guess the only thing that leaves is the air-injection reed valves that vent into the exhaust system. But will the reed valves be sufficient to prevent back-flow into the crankcase, apart from the PCV valve?

All comments, perhaps apart from the "factory did it right, so why mess with it" variety would be most appreciated. Actual experience would of course be valued most of all.

Thanks!

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Never Mind Air Injection, What About a PCV System? 1 week 5 days ago #27859

  • stocktoy
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Personally I found the OEM crankcase vent system on these bikes (for me and my very heavy throttle hand) always caused high oil consumption (due to quick throttle app love the sound of my DG header exhaust system) at least on my 79's so I just ran a fuel hose from the vent pipe out the back of the bike under the seat to get it that seemed to fix the oil consumption to a certain extent away from the bike. just my two cents worth.

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Never Mind Air Injection, What About a PCV System? 1 week 1 day ago #27885

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So basically you're talking about the old pre-'67 "road-draft" system of crankcase ventilation? I'm not against that, per-se, for bikes that were built with it, but any engine will benefit from having a crankcase ventilation system that draws the corrosive vapors out of the crankcase. This would consist of a vent high up on the cam covers, with an PCV valve to limit the amount of air flow, and more importantly, that would incorporate a blow-back valve that would prevent a backfire from the intake system from igniting the fumes in the crankcase with catastrophic results.

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Never Mind Air Injection, What About a PCV System? 1 week 1 day ago #27886

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The USA Canada Spec KZ1300's had the whole Clean Air System fitted with the Reed Valves in the cam covers, the valve itself with the pipes from the Air Box and the Inlet Tracks.

The Euro Model did not have any of this fitted.................nothing, yet the bike is identical.

When most owners in the UK buy an imported KZ1300, one of the first jobs is to get rid of the whole system and block the reed valves off and plug the large hole at the top of the air box that the valve feed pipe was connected to.
After this, the bike runs exactly the same with no increase or decrease in power or any other noticeable difference.

This is also the case with many imported bikes with the "USA / Canada Regulation" system fitted including the ZRX1200 Models, which again owners get rid of as soon as they buy the bike. The ZRX1200 Forum call the the system the "Octopus" as when its removed and lying on the floor, it looks like a dead one !!

Just get rid of it as if not its just more stuff to go wrong and cause potential problems.

Pete F
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Why Have Four When You Can Have Six ?

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Last edit: by strate6.

Never Mind Air Injection, What About a PCV System? 1 week 1 day ago #27887

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One other thing my bikes did not have this thing on the valve cover they were just clean valve covers no extra stuff on the top of them. Guess I was luck to get early models of the 79 model.

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Never Mind Air Injection, What About a PCV System? 1 week 1 day ago #27888

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Stocktoy,

You were lucky with these............they are the best type and have more room for removing and refitting the tank than the others.

There are 3 types I have found over the many different 1300's I have owned and worked on.

USA / Canada have the short OPEN ports on them for the rubber pipes to push onto.

Euro UK type are either as above but with the ports blanked off as not required.

The rarer Euro / UK Flat Type like yours which have no ports at all.


Pete F
UK
Why Have Four When You Can Have Six ?

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Last edit: by strate6.
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