670 Mods(how Much Power?)

[oldyeller]

Just got my 97 670 back from Don Emery Performance(DNE Performance).I had a rotary valve seal go bad on me so I took it to him to repair.While it was there he added a shim kit under the cylinders ,cut the head so it has .065 squish and added a 501 rotary valve and a shortened Y pipe.Anyone had this done or know how much more zip this will give me?

[paidncash]

my cousin has that done to his 670 and it's fast you should like.But it still wont beat my 670 HO.

[ballsout1]

I had a similar set up on mine, would guess 127 to130hp What are you using for clutching?

[oldyeller]

Sled was completly stock.Any additional suggestions are welcome.A friend of mine has a HO but its not studded so its hard to compare.We never ran them head to head but I know his has big top end.Also can I take the clutch off of this sled while the engine is in the chassis.When I was pulling the engine I pulled the clutch first but there wasn't enough room to get it off.I didn't try real hard though as I was pulling the engine anyway.

[mr670]

oldyeller you probaly picked up 6-8hp(what did DNE tell you?) Bondi engine's has a kit for the 670 that puts out 144hp.

[ballsout1]

Whats up with pulling the motor to take the clutch off? Pm me I have clutch set ups for that sled if you want.

[oldyeller]

I didn't ask Don what kind of power to expect as I have seen similiar tune-ups done in magazines and they were in the 5-8 hp range like you say.I've never seen that exact setup done though.What alls involved in the Bondi setup.I've seen a dyno test in race and rally (snotech) and they got 140hp with dual pipes.Unfortunately they put the pipes on first so it was hard to tell how the much the other mods would add with the stock pipe.This is just a trail sled not a racer but since it had to be completley torn down to replace the rotary valve seal I asked if he had any little "improvements" he could do while it was apart that wouldn't break the bank and keep it trail happy.One thing I haven't put on it is the short rubber boots for the carbs.There supposedly good for a few hp but I've also heard you have to watch the injection pump arm doesn't get caught up in them.

[mr670]

The 144 Bondi Engine consists of heavly ported cly and cases and is a trail engine, stock pipe. I have 4500k on mine. I hate to tell you but you don't have to tare down a 670 to replace R.V seals, tha job can be done with the engine in the sled.

[mxzx670ho]

First off cutting the exhaust doesn't do anything! I know several world record holders that run 670's and 670ho's. The best and cheapest thing for that motor is the thinner head gasket with that you get about 6hp. The shorty boots well the shorter boot gives you more low end torque not horse power, but you lose top end.Fuel mixes better with the longer boots. So the way to get the same thing is clutch it. and clutching it can give you low end and top end with the right gears and ramp, pin, spring and helix.. And straightline performance has the parts to make that happen. and for cheap than most all other kits I've priced out.



MXZX440 Sleeper. You'll find out if you can catch me

[jaedymack]

Ok........i have the dyno sheets on my 97 670....The last thing i did and I put it on the earlier post was cut the Y-pipe.......Dyno at St johns, MI....4 hp....got the pipe cut for $25...followed DNE's guidelines...Updated carbs to 98 670 settings....3 hp...You want to put a thicker base gasket not thinner to raise the port timing...no sense of doing that if you arent going to get the head cut...Cometic 8mm base gasket....$13.00...I got my head cut for $20 to .065 clearance....short boots...501 RV valve...Roller clutch kit....stay with single pipe...I tried 44 mm carbs could get right jetting so went back to 40mm carbs...Sled runs well....