3XV01 questions

[JKV45]

Are the compression numbers in the service manual correct for the 3XV at just under 100 psi, with a minimum of 70 psi?

Seems really low.

Also, should a 3XV01 have restrictor plates in the airbox and boots?

Thanks.

[thump566]

As far as I'm aware, there should be no should be no restrictor plates in the airbox, not sure what you re referring to as the boots? If you mean the rubbers between the carbs and the airbox then again, the answer is no, There are however minor differences between the airboxes on the R/RS/SP and SPR airboxes as shown in the images attached.

[JKV45]

Thanks.

This thread by busa 1300, post #117, shows his airbox and boots that look to have a restrictor -

https://pure2strokespirit.net/forums/index.php?topic=6141.105

I was under the impression that a restricted 3XV would have them.  Mine does not.

[thump566]

Ok, I see where you are coming frpm.

The intake boot between the carbs and the airboxes differ depending on the model as the carb size body necks differ. There is no difference between the R and SP upper airbox as far as I know other than a slightly less restrictive intake at the front of the SP version.

There are far more experienced 3XV owners on here than me so hopefully others will add to your thread.

[ybk]

SP models have the restrictors in the intakes (between carb and airbox) like you saw in Busa's thread. The SPR's don't have them which is why they are sought after.

The R intakes don't have any restrictors, they are just smaller.

SP and SPR top airbox lids have straight intakes and the R type is tapered.

[JKV45]

Thanks guys.

What about the compression?

Is 100 psi really the correct amount for a 3XV?

[ybk]

@JKV45 that's what the manual says...I agree usually it's higher

[JKV45]

@JKV45 that's what the manual says...I agree usually it's higher

I did the math (conversion to psi) a few times, and 100 psi is what I came up with, but it seems a bit lower than I would expect.

Thanks.

[busa1300]

I'm pretty sure I had a bit over 140 in both cylinders on my well worn 3XV2 when I was first trying to get it going. 100 seems to be maybe the lowest, before doing a rebuild?...or is that supposed to be a typical average compression?
Also, you should use an adapter that is the same thread length as the plug. If it's a long thread length in the head and you use a short tester, it could possibly change the result?

[JKV45]

I'm pretty sure I had a bit over 140 in both cylinders on my well worn 3XV2 when I was first trying to get it going. 100 seems to be maybe the lowest, before doing a rebuild?...or is that supposed to be a typical average compression?
Also, you should use an adapter that is the same thread length as the plug. If it's a long thread length in the head and you use a short tester, it could possibly change the result?

According to the manual, 100 psi (7.0 kg/cm2) is the standard reading, with 71 psi (5.0 kg/cm2) being the minimum.

I got 85 psi when kicking it over briskly with both plugs out. I have heard of others using a drill on the crank to spin the engine faster.  The manual says 700 RPMs.  Not sure how you would know. 

It also says to warm the engine, then remove everything, before taking a reading - which I didn't do.

[busa1300]

Try with just the one plug out for the adapter. I know it makes a difference on RGV's with the center seal.