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questions about xv700 to xv1000 engine swap.

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questions about xv700 to xv1000 engine swap.

PostAuthor: motorlou » Sat Aug 10, 2019 9:52 pm

hey guys just had a question about swapping out a 700 to 1000 engine (both 1985). i want to know the differences in the tci unit. besides timing curves, i read you are supposed to use the pressure sensor from the 1000 along with its cdi. what is this sensor? where is it located. what does it sense?. on the xv1000 tci there are a few extra pins than the xv700. one for the kickstand relay(black/white) then there are red/white, black/red, and black/yellow that go to the said pressure sensor. can the sensor be bypassed? if so how? can an xv1000 tci be used on the 700 or vice versa?

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Re: questions about xv700 to xv1000 engine swap.

PostAuthor: Flyingdog » Sun Aug 11, 2019 12:40 am

About the pressure sensor..just another one of those EPA demanded parts, so the bikes could be sold in US..or any other place having emission regulations. It'll be located sitting ontop of the coil cover. During deceleration, it will pull vacuum and retard timing abit. Eliminating some backfiring. IMO: bout as worthless as the MCV/AIS, or any other emission garbage. And..yes..can be eliminated if it don't work or you just don't want it. Some will say it's needed. That's cool, but I say if it is, it's usually to masked something else. But that's just "my" side. Haven't had one on the 1000 since the 80s. Never a problem. I just removed/plug the vacuum hose at the "source" and clip the wire. Been soo long, don't remember how far back I clipped it. Probly at the TCI. If you look at bikes thru out the years, you'll notice how they (Yamaha in this case) kept adding things to eliminate problems pop'n up. Mainly..back fires. All this stuff cropped up, when the "save the earth" movement came to full swing. Think it was around the time hair spray was kill'n the ozone... :bg: Certain years got the MCV, some AIS, some deceleration valves on Mikuni carbs...some a combo of everything. All-in-all..I look at it as anything extra put on a carb..usually ( I say usually) will give ya fits sooner or later.

#36---> https://www.yamahapartshouse.com/oempar ... ectrical-1
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1981 xv750 Virago
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Re: questions about xv700 to xv1000 engine swap.

PostAuthor: motorlou » Sun Aug 11, 2019 1:59 am

thanks for the chime. this being said, i believe i can use either tci in either motor. i cant see any differences in the engines except bigger displacements? the pick up coils even look the same (other than the pin connectors being in different positions at the tcis i think i like the 700 tci better because it just has less pins to deal with. i use my bike to commute everyday so i cant just begin swapping stuff on it. but i definately want to answer these oddball questions i have about electrical parts interchangeability.

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Bike year & model: 1985 virago xv700 and 1985 virago xv1000
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Re: questions about xv700 to xv1000 engine swap.

PostAuthor: Arjay » Sat Sep 07, 2019 10:33 pm

Man, you guys are singing my tune. I messed my xv1100 virago tci when swapping engines pinched/shorted the wire to the pressure sensor. Now I got no spark and no fuel pump, and yes been all through the safety shut off and clipped the wire at the tci.

What keeps crossing through my mind is look how cheap the xv250s are, I imagine they are 2 cylinder and Yamaha dropped 2 pickups for 1. One pickup works because sparking is done on tdc compression and tdc exhaust and I think the timing is done from two metal strips on the flywheel. (reluctance), first strip is before tdc, to measure speed against second strip at tdc. Or maybe the measure is last tdc then first strip, whatever, point is I think the 2 strips establish engine speed. So maybe pressure sensor isnt needed.

Currently, the price of a guaranteed xv1100 tci near $400 after mailing and taxes. but that would include all safety features and fuel pump handling.

If I skip safety features. Side stand down+in gear=off. Side stand up + in gear + clutch released = no start. Also fuel pump shuts off when gas is low until put in reserve.

So, skipping the safeties, I could use ignition portion of tci only. Hook fuel pump to power off main key switch or after kill, and rest is normal battery/reg-rect and lighting.

Is this wrong? Im thinking they might have monkey around with the reluctors spacing, but tdc is tdc ad rpm is rpm and dwell is dwell..

Because Ive seen some used ones as cheap as $15.

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Re: questions about xv700 to xv1000 engine swap.

PostAuthor: Arjay » Sat Sep 07, 2019 10:54 pm

motorlou wrote:hey guys just had a question about swapping out a 700 to 1000 engine (both 1985). i want to know the differences in the tci unit. besides timing curves, i read you are supposed to use the pressure sensor from the 1000 along with its cdi. what is this sensor? where is it located. what does it sense?. on the xv1000 tci there are a few extra pins than the xv700. one for the kickstand relay(black/white) then there are red/white, black/red, and black/yellow that go to the said pressure sensor. can the sensor be bypassed? if so how? can an xv1000 tci be used on the 700 or vice versa?


Pre 1990 has 2 sensors (reluctors). so your years matching is good. both tci will handle 2 sensors. You will want to use your 700 tci if your wiring trunk still has tci connectors. In fact whatever safety features your 700 had, you'll still have.

Ignitech has a nicd solution though, the programmable model can include the ressure sensor if backfiring becomes an issue. Model Sparker Tc4
http://www.ignitech.cz/en/vyrobky.htm

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