only got '85 XJ 650 4KO

**EDIT to titel of thread: "Only got 43HP on '85 XJ650 4KO**


Hi all.
I am a total beginner with motorcycles, and have had the bike since the start of this season.

I had my XJ650 to the mechanic, to troubleshoot it: It smelled like gasoline, and an associate of mine, who knows about motorcycles, thought that ran a bit too rich.

The mechanic took it onto the Dyno, and did a 4gas-measurement, and compression test.
It turns out, that it didn't run too rich, but on the other hand, the carbs were out of sync. They got synced, and now it runs a lot greater.

However. The pictures shows the results from the Dyno, and compression test (the small scrap of paper on the first picture).

The compression test was very fine, he said.
But it only had 43HP on the gearwheel, which is quite far from the 72-ish HP on the motor. I am aware, that there should be a decrease in HP measuring from motor to rear wheel, and on top of that, it doesn't run original exhausts. I have a 4in1 MOTAD Mxj6, which when I look up online, is actually meant for the XJ 750 (http://www.bits4motorbikes.co.uk/Exhausts/MotorbikeExhausts.html?MotorID=1140).
But can that exhaust really be the reason for such a decrease in HP?

So my question: Is 43HP on rear wheel a surprisingly decline? It's an old bike, with 23xxx km on the clock, and with non-original exhaust?

Theres probably a lot of factors to take into account, like the state of the bike, the engine etc., but I am interested in hearing what you guys think!

The Mechanic thought that the bike ran good, and he wouldn't worry about the few HP, and that I most likely wouldn't really notice a difference from 43 to fx. 53 HP, and I dont disagree with him, however I am curious about how your bikes perform

And btw. I have inserted a few images of my old lady as well, because... well do we really need good reasons for showing our bikes, new or old?

Many thanks

Niels Keiser Jacobsen, Denmark.

 

Welcome aboard , there are a few items that come to mind , on why your HP is down , Jetting on your carb is one item. With an aftermarket exhaust you need to go up 2 sizes . From your pictures you look like you have stock airbox ( that is great two thumbs up) make sure your filter is clean and sealed correctly. The other thing are these the correct carbs for your bike (IE did P.O. put something else on bike?) Have you adjusted the valves? There will be a difference between the crank HP and rear wheel but doubt it would be that much. Just some random thoughts.

 

Thanks for the reply.
To be honest, I don't really know a lot about the previous owners, and what they have done to the bike, other than the current engine has replaced the engine that was originally on the bike, and therefor the low Km on the clock.

The filter got changed this winter, and it sparkling clean. I don't really now how to be sure, that it is sealed correctly. When I took it out to inspect it, I thought that it was surprisingly difficult to maneuver it in place, so it sealed up tight, since I needed to put the "top of the airbox" in place, in order for it to seal up around the air intake. Don't know if this answer makes any sense .

I have no idea what size the jet needle is. But it needs a bigger size, to allow more fuel in, in order to keep up the power?
The 4-gas analysis said that it looked fine though, and the mechanic didn't really mention re-jetting as a feasible option, maybe because it would cost me a lot, to get him to do it

Airbox: Yes, I would never even consider changing them, after reading about all the hassle people have had with them!

 

Recommend , pulling your valve cover and check valve clearance .. You only need a zip tie or a piece of romex wire to pull shims . Click on this page on upper right corner xj4ever this is Chacals link read information over load hr . There is so much info this should help you along the way .

 

+1 on the valve shim check
you mention synced but not color tune (fuel mixture adjustment)
before you rejet any thing look at your spark plugs post a photo of them .

 

Ah sorry, maybe I haven't been clear enough in my original post.
The mechanic did a 4-gas analysis, and check if the fuel mix was optimal. I thought that it ran too rich, but when he measured it (I don't know the details of how to do it), it was actually running fine. A bit too rich on the very rpm's but he didn't really believe that it would be worth the hassle (Read: my money), to adjust it

It should def. check up on the valve shims. Say if I adjust the valve shims, do I need to adjust something else as well? Like would my jetting have to be remade after?

Many thanks

 

checked but did not adjust.gas analyiss. well unless your 4 to 1 exhaust has access bolts on each exhaust pipe he was reading the collective of emissions at the tail pipe
valve shims is first step to everything.
then sync carbs and adjust fuel mixture on each carb. easy way to adjust mixture is with the colortune tool. next is if you have a real good ear.
all still require looking at the plugs for fuel deposits on tang

 

He did look at the plugs, and mentioned, that he cleaned two of them.
Would this be the access bolts? But then again, I'm not sure wether he measured on each carb, or just the collective emission.