engine swap question

[chaz]

I am currently fitting a 1998 motor into a 1997 bike but have come across a problem...
the 98 motor uses the PAIR system wheras the 97 does not. I assume its the PAIR as theres an extra bit under the air box with pipes from the rocker covers.
the bike wont run unless its on choke, and when the throttle is operated it stutters.
my guess from the plugs is it is running lean due to extra air from the PAIR system..
can any one confirm, would I need the black box from the 98 bike?
can I just get away with putting the old covers and air box on or do I need to swap back the original carbs.?
finally, crank position senser, are they different for each engine?
thanks

[Phil-VTwin]

The PAIR system is not present on offiical UK bikes, what you are seeing are the crankcase breather pipes that stop the build up of pressure within the engine, however i wasnt aware the 97 model didnt have these!

Are there 1 or 2 pipes on the rocker cover?

[chaz]

the confusing thing is Haynes states PAIR in one section and EVAP (California) in another section.
on the 98 motor there is a Pair control valve screwed under the air box. pipes from both covers come out of plates in the tops of the covers and straight into the pcv and a small vacuum pipe from the front carb.
Both covers also have normal nipple style outlets which pipe straight into the air box,
the old covers that came off are the same as my own 97 version with just the single pipes from the nipples into the air box and no lug under to screw the pcv onto. Both covers on both 97 motors (mine and the broken motor) have the plate holes not drilled or cutaway but the profiles are there.

[chaz]

swapped covers and airboxes but still runs rough and better on choke.
so its down to carbs change, or crank positioner change then?

[gilson]

swapped covers and airboxes but still runs rough and better on choke.
so its down to carbs change, or crank positioner change then?

Have you balanced the carbs? I'm sure you have to do this after putting them back on.

Also pictures would help...

[tony.mon]

I'm sure you would have checked it, but could there be an air leak, or perhaps a split inlet rubber?
Also check vacuum pipe for leaks.

This would certainly give the same effects as you describe.

Secondly, I seem to remember that the Factory pro Jet kit I fitted came with different recommended settings for a bike fitted with PAIR, maybe there are different carb jets/settings?
If so it might be easier to track down a set of carbs for a PAIR type engine, if you can...

[chaz]

the engine came with carbs, airbox oil cooler all fixed to it.
now swapped over to the old airbox and rocker covers off, will see what happens

[Phil-VTwin]

Chaz, how sure are you that the replacement engine is 100% ok?

[chaz]

can someone tell me why there are 2 small connection nipples on the fuel tap??? thought I put it back on the right one but missing and starved of fuel!!!
I put the vac pipe on the one pointing down, 2 hours later I read the Haynes manual now Ive connected to the one on the back at 90 degrees and the motors running good.
WTF is the other one for as I dont have a pipe to go on it??

[goody]

Honda put it there knowing that it would confuse 50% of owners and they'd put it on the wrong one causing the bike to run terribly. They would then have to take the bike to a Honda dealer who would charge them 2 hours labour for putting the pipe on the right connector. This would keep their dealers happy and restore owners faith in the Honda brand.
Then along came the internet and owners forums and screwed it all up for them.

[gilson]

It more like 90%....

[sirch345]

WTF is the other one for as I dont have a pipe to go on it??

There is not meant to be a pipe for that (at 6 o'clock on a clock face) outlet, all it does is allow fuel to drain out if a split occurs in the tap diaphragm.

Chris.

[bikerpiker]

I think it was Jazzscot that posted this pic previously ............

[chaz]

thats the one, hanging down like a spare you know what!!

nice explanation about the overflow/leak

[tony.mon]

Might be right, but why allow fuel to flow out onto the rear exhaust area? If that were the case Honda would have fitted an overflow pipe as standard like they have with all other possible fluid overflows, surely?

Seems to me it's there to allow air in behind the diaphragm.
Otherwise, if it were sealed, the diaphragm would effectively push against an air "spring" and would have resistance against opening.

Not that it matters, it's a bloody red herring that catches everyone out some time or other. They should (if I'm right) have just drilled a hole and left it like that.

Might just hacksaw the thing off next time I have the tank up....