Exhausting question???

[wolfe 21]

When I bought my 400 the previous owner had removed the spark arrester/baffles from the exhaust. I have recently had to take the carb apart to clean it due to me having not ridden/started/moved it in about 8 months and found it had what I assume to be stock jetting (38 and 140 I think, main was not a concern at the time so I wasn't checking too close). Anyway, I've just been told that this gutted exhaust could lead to top end damage, especially valves. This set up has maybe 15-20 hours of riding after the arrester was removed, usually medium pace on gravel roads or tight woods trails in 1/2. My question is simply how far gone am I right now?
I've noticed it's hard to start and keep idleing, but I've always attributed that to the factory jetting (I never wanted to tear into a $3000 investment to change jets unless I had to). Anyway, I will be replacing the exhaust with a stock pipe with baffles/arrester next week, but I'm afraid the damage is done now.

Thanks, James.

[riotact]

Put in a 145 main and 40 or 42 pilot and see how it does.I dont think it is damaged.Just get it right or as close as you can so it doesnt lean out on you and cause you damage.Does it backfire when you are moving and let off the gas?If it pops,you need to turn your mixture screw out or go up in pilot jet size.

[4reeds]

its not hard to replace the jets. have you adjusted the valves,or the idle adjustment?those motors are bullet proof.they are hard to destroy. do a tune up,valve adjustment included, check to see what jets are actually in it.

[wolfe 21]

After I replace the muffler, both for the baffles and to have a quieter more neighbor friendly system, a full tune up is next on the list. New plug, adjust valves, check ignition, etc. I think I'll take it to the shop for the jetting and tune up. I'd rather know it was done right than chance me cobbing something up.

Riotact, sometimes it does pop when I let off the gas when I'm moving so I'll definitely have to adjust the jetts. I'll wait to see how much the restricted muffler helps before changing things too much.

Thanks,
James