XJ650 Turbo No boost, bogging at 6k+

Hey everyone, first time posting after lurking a bit while restoring my 650 turbo, I got it running and driving really well but once it starts to build boost at 6k, it starts to bog down as if it’s running out of fuel, the boost gauge starts going towards the green but stops right before actually gaining boost. I do notice a leak at the surge tank drain and from the left exhaust leaks black oil, i cleaned the oil check valve, and tested the pressure and knock sensor they work great. New spark plugs as well, new fuel lines with a filter, petcock rebuilt with oem gaskets. What else should I check? is the turbo bad? the turbine had zero play and spun freely and it does drive completely perfectly before boost.

 

Possible issues:

a) wastegate actuator frozen and/or wastegate seized "open" and/or vac tubing to wategate actuator can broken/missing/etc.
b) reed valve insalled upside down
c) other carb or electrical problems
d) something else.......

 

I struggled with similar conditions.
A regular style fuel filter was the culprit. A hi-flow filter is required for turbocharging
Since you just installed this, try removing it.

 

Is there a specific filter/filter style you recommend? I just put on a paper fuel filter I had spare from other bikes, would make sense that it would be starving the carbs from fuel at boost

 

I currently rely on the petcock filter and the screens in the carbs.
I think as long as the fuel filter says hi-flow turbo application you should be good.
But again, easiest to just eliminate it for now.

 

Took off the fuel filter and it’s bogging a lot less but still no boost, just floats right at the start of the green and starts to bog around 7-8k, i’m seeing smoke coming from the exhaust connector after the manifold, the 4 to 1 into the turbo on the 4 clamp ends, i’m guessing it’s the check valve issue with oil but would that signify an exhaust leak and to change those out? would a leak cause no boost?

 

wastegate moves good, and carbs have been redone completely, haven’t checked the reed valves i’ll do that and update thank you!

 

oil pooling in the turbo unit is a common problem. Most assume the oil check valve is leaking but I found mine was working correctly.
Mine was leaking oil through the scavenge line. I believe the rotating surfaces in the scavenge pump wear, allowing seepage while at rest.
The easy fix for this is installation of another check valve in the scavenge line.

Any exhaust leaks will diminish boost pressure so start there. Make sure all pipes are tight at the head, everything tight at the collector etc.
@chacal mentioned the wastegate, make sure exhaust is not leaking there.
@chacal mentioned the vac hoses, make certain none are dislodged.
Check the air pipe from the compressor to the surge tank is all tight.

Make certain your fuel pump is working.
With the motor off, put it in gear and press the starter, the bike shouldn't turn over but you will hear the pump running and hear the fuel squirting back to the tank.

If you go to my thread starting at bottom of page 9
https://xjbikes.com/forums/threads/simmys-naked-turbo-project.110254/page-9

You can see the steps I took to verify the auxiliaries to diagnose a bogging issue similar to yours.
The pressure regulator needs to keep fuel pressure 2.8 psi above boost pressure, or 2.8 psi at idle.

@chacal sells a kit to rebuild the surge tank drain fitting, I almost guarantee you will need to rebuild that.

 

The turbo oil pumps is basically "2-pumps-in-one"....the regular positive-pressure pump for engine bearings, etc. and a negative-pressure pump for scavenging the turbo. There is an oil seal internal to the pump that "seals off" these two areas:

HCP22877 Aftermarket oil pump scavenge port-to-crankcase RUBBER SEAL, fits all XJ650 Turbo models. This round “donut” seal fits onto the oil pump housing (over a dowel pin) and seals the scavenge pump to the oil pan. NOTE: if you are getting a leak under the bike, you can confirm whether this seal is the source via disconnecting the oil line from the outside of the oil pan (leave the oil in), and insert some 6mm OD clear tube through the pan and into the oil pump (thus by-passing this gasket). If oil leaks around the outside of this tube, then it’s this seal that is leaking. If the oil leaks from inside the tube, then the leak is internal to the pump, and is probably due to a worn or damaged HCP27594 shaft seal. Use 1 per engine. Each:
$

HCP27594 OEM oil pump DRIVESHAFT OIL SEAL. The metal-cased seal fits into the spacer plate in the oil pump around the pump main shaft. Failure of this seal (typically caused by a sticking pressure relief valve in the pump) will allow oil to flow back to the turbocharger via the return line, thus filling up the exhaust when the bike is stored for more than a day or two. NOTE: this seal fits very tightly into the spacer plate, and it is advisable that the spacer plate (which is aluminum) be heated up with a heat gun, etc. to allow the aluminum to expand, before attempting to “pop” the metal casing of the oil seal out of its cavity. Be careful to not scratch or gouge the spacer plate when prying! Each:
$

 

The drain on the surge tank does look to be leaking, both from the drain itself and at the end of the hose leading to the ground, i’m guessing the leak at the drain itself could cause pressure issues? i’m gonna take off everything intake and go through it all, i noticed the airbox with the element has some play even with it clamped and screwed in. i’m using an oem style filter i made using uni foam and a 3d printed housing to match oem housing. fuel pump seems to work good, the bike does run perfectly until it reaches boost RPMS, will update after checking intakes

 

Update, took apart the surge tank and the intake, it looks like either gas or oil is getting in the surge tank/air cleaner, and the drain valve and at the reed valve are leaking fluid. seems like it’s getting to the carbs as there’s residue on the carb where it connects to the surge tank. all the boots connecting to the turbo are also leaking. Any ideas on what it means and what to look for? I’m going to further take apart the intake and inspect everything. I’ll need to rebuild the drain valve and the gasket at the reed.