Help! 1994 DT225 bogging down... loss of power

[Mcgou471]

It has been with a great local Suzuki mechanic and hes beginning to get stumped. Motor idles great, and will run good until around 4k RPMS and then it boggs down. I can bring it back to idle and then hit it again and once I hit the RPM range it will bogg down to pretty much nothing again. He has checked fuel pumps, compression, and all computers have been replaced. All plugs have been replaced. All filters have been replaced and still having the issue. Injectors have been sent off and checked as well. Is this a known issue? Any ideas?

[Solarman]

Being specific and clear in your details helps us on this end of the screen. We are looking at this from what you tell us.
Does motor bog at 3500 rpms, or 4k? Sounds almost like neutral safety switch? Did they have one on your motor? It limits rpm to 3500 if it thinks it's in neutral.
Your details, not being real clear, but have mentioned you have injectors, so you could have a bad TVS, or possibly a bad magneto coil (the high speed condenser charging coil). Both of these can be tested by the Suzuki service manual.

Also, you mention he checked fuel pumps, did he check the check-valves (2 clear discs), located in the lower section, of low pressure pump(s)? These discs are not included in rebuild kits, but often fragment in these older motors, sometimes blocking the float needle valve (restricting fuel). Also, there might be a small screen filter at the bottom of the VST, inside the line that feeds the HP fuel pump? Was this checked?

Good luck, post back when able to let us know how it's going.