Free & Cheap Mods

[660r2a400ex]

I am on a budget and need more top end This is what i am doing.
Degree Key - $23-what will i gain?
Grinding Exhaust Welds - FREE-what will I gain?
Cutting Out Choke w/ #42 pilot jet - FREE and $5-what will I gain?
Hole in air box - FREE-what will i gain?
race cut fenders( does this help top end? more aerodynamic? less air resistance?) - FREE
total price for mods $28 What will be my total gains in low,mid, and top end?

[xc400ex]

With all those mods you should get a great boost in throttle response provided you jet it properly. Another thing you can do is pull off the top end and use RV sealant for the base gasket and use 1 layer of the stock headgasket. This will give you a better quinch area around the head resulting in the motor running cooler and more power.

[Raptor4439]

I was thinking about shaving my front fenders but I didn't think it would help that much, can someone tell me what I could gain from it?

[sickmojave]

Originally posted by 660r2a400ex

Grinding Exhaust Welds - FREE-what will I gain?


I did this and did not gain a thing.I think this would only help if you have the head ported and it's not free because you will need to change the gaskets.

[sickmojave]

Originally posted by xc400ex
With all those mods you should get a great boost in throttle response provided you jet it properly. Another thing you can do is pull off the top end and use RV sealant for the base gasket and use 1 layer of the stock headgasket. This will give you a better quinch area around the head resulting in the motor running cooler and more power.

#1 how did you compensate for the fact that it retards the cam timing?

#2 how does it make it run cooler if it makes more power?

cutting your front fenders does increase topend which I dont think you would notice...it does however help you to see where your tires are pointed at during trail riding....it also looks cool

[02Yellow400]

yeah the only thing your really gonna notice is the throttle response. It will be alittle more snappy. As for that degree key. I havent heard many good things about them except for save your 23 bucks.

[wilkin250r]

Originally posted by sickmojave
[B#2 how does it make it run cooler if it makes more power? [/B]

Heat is generated by burning fuel. In theory, a high-compression motor generates the same amount of heat as a low-compression motor, because they are burning the same amount of fuel. However, the high-compression motor will have more power.

By properly setting up the squish band you engine can remove heat from the compressing fuel/air mixture. Removing heat means your bike runs cooler.

However, I'm not entirely sure the method he describes (removing the base gasket and a thinner head gasket) will work with the stock piston. You would need to check your piston/head clearances very carefully.

[sickmojave]

live and learn ;) but this makes me wonder why you can't run a sparks key with a higher compression piston :confused:

[airheadedduner]

Originally posted by wilkin250r
Heat is generated by burning fuel. In theory, a high-compression motor generates the same amount of heat as a low-compression motor, because they are burning the same amount of fuel. However, the high-compression motor will have more power.

By properly setting up the squish band you engine can remove heat from the compressing fuel/air mixture. Removing heat means your bike runs cooler.

However, I'm not entirely sure the method he describes (removing the base gasket and a thinner head gasket) will work with the stock piston. You would need to check your piston/head clearances very carefully.
I don't think that is possible with a thumper unless you run a piston with a different dome/crown shape. You can't really set the squish by filling then milling the head because with valves there is no room to do it properly.

[wilkin250r]

Originally posted by sickmojave
live and learn ;) but this makes me wonder why you can't run a sparks key with a higher compression piston :confused:

It would take a while to explain, so I'll just sum it up. When you increase compression, it will speed up the combustion process. If you speed up the combustion process, AND advance the spark timing, you could get a detonation problem.

If you want a full explanation, PM me or start a new thread.

[wilkin250r]

Originally posted by airheadedduner
I don't think that is possible with a thumper unless you run a piston with a different dome/crown shape. You can't really set the squish by filling then milling the head because with valves there is no room to do it properly.

And thus my last line, that I'm not sure the process would work with the stock piston, because the tolerances may already be set correctly, and really don't have any room to get closer together. I don't know for certain, you would have to ask Mickey Dunlap or another engine pro.

[xc400ex]

#1 how did you compensate for the fact that it retards the cam timing?

I didnt....


#2 how does it make it run cooler if it makes more power?

Actually I didnt think it would work with the stock piston either but im some post I read where mickey dunlap said it would work and recommended it.

[Quadfather]

Originally posted by Raptor4439
I was thinking about shaving my front fenders but I didn't think it would help that much, can someone tell me what I could gain from it?



A face full of mud.

[airheadedduner]

Originally posted by wilkin250r
And thus my last line, that I'm not sure the process would work with the stock piston, because the tolerances may already be set correctly, and really don't have any room to get closer together. I don't know for certain, you would have to ask Mickey Dunlap or another engine pro.
From what I understand about the squish band it needs to be quite large to be effective for most aplications. On my R when CT did it I would say it was at least 50% bore size. I have heard on fixed gear shifter carts they run as far a 75% bore size:eek2: One of the main ideas behind it they improves combustion and prevents detonation is that it forces the fuel/air charge in a concentrated spot usually centered around the spark plug.
By forceing the fuel charge in a concentrated area it is more thuroghly and rapidly burned. With out the proper squish fuel at the outskirts of the piston crown don't get burned as rapidly, usually not till after TDC(advanced timing can correct this but produces some more heat). If the fuel charge is not burning completly till after TDC that fuel is not producing power in the most efficient way and is producing excess heat that can lead to detonation.

To me it can't really be applied to thumpers, the valves are in the way and it can't be done properly. Even the pryimid shaped pistons don't replicate a squish band. In fact, IMO they do the opposite. I am no expert on thumpers, I am still converting over from 2 smokes. We need Mickey in here to clarify it. No flames though, I like were this is going. Good info:)