Bigbill
Husqvarna
Pro Class
The change over to LQ allows to run more port timing without damage to the engine, because of heat that's generated.
My early '84 250wr AC has the cr cylinder. She's a tad more pipey over the '83 250wr. It's still a 250 but more fun to ride.
On my '81 250cr the last of the 70's engine. I raised the exhaust port and polished the port. I knife edged the rib in the transfer ports. I also port matched both transfer ports and funneled them more so the flow (gas mix) has a easier path when it starts to flow into the transfer ports. You can see that some cylinders in the transfer ports are uneven do to the casting. I funnel or flare the beginning of the transfer port and blend it into the port then polish the entry section. You can make changes to the rib in the transfer port too. I knife edge it and change the straight knife to a half round open c type shape. This keeps the forced gasses more to the middle of the port for even flow. I also advance the timing a tad to enhance the port timing. I run a 53T rear sprocket with a 11T front. With the UFO installed in the carb slide. Now this does narrow the power band but she's an animal on the mid to top end.
To me the 390cr has a wider power band from the bottom to the top that bigger bore doesn't like going slow. She will chug, chug when it's close to idle. But it has plenty of front wheel lifting power in any gear just twist it.
My early '84 250wr AC has the cr cylinder. She's a tad more pipey over the '83 250wr. It's still a 250 but more fun to ride.
On my '81 250cr the last of the 70's engine. I raised the exhaust port and polished the port. I knife edged the rib in the transfer ports. I also port matched both transfer ports and funneled them more so the flow (gas mix) has a easier path when it starts to flow into the transfer ports. You can see that some cylinders in the transfer ports are uneven do to the casting. I funnel or flare the beginning of the transfer port and blend it into the port then polish the entry section. You can make changes to the rib in the transfer port too. I knife edge it and change the straight knife to a half round open c type shape. This keeps the forced gasses more to the middle of the port for even flow. I also advance the timing a tad to enhance the port timing. I run a 53T rear sprocket with a 11T front. With the UFO installed in the carb slide. Now this does narrow the power band but she's an animal on the mid to top end.
To me the 390cr has a wider power band from the bottom to the top that bigger bore doesn't like going slow. She will chug, chug when it's close to idle. But it has plenty of front wheel lifting power in any gear just twist it.
