View Full Version : 500R Decompression Release?

06-25-2006, 11:06 PM
I apologize for the excess amount of threads but I felt this couldn't wait. I have seen in many old threads that when people did the ATC500R conversions they put decompression releases or something of the sort. Can anyone relate to this? This would be really good for my 85 CR500 and then my 86 ATC500 project that I am starting. Any sites or any info will be helpful. Thanks...

06-26-2006, 03:09 AM
Decomp's on 500's are for pussy's...unless you have an Extremly high-compression motor....Get a leg...lmao...

06-26-2006, 10:42 AM
Well my 85 is already a pain in the ass to start but I am going to have some porting work done, bore it to the next oversize, thinner gaskets, probably lower the exhaust port, and some other little things so yes to answer your question it will be a extremely high compression motor.

06-26-2006, 11:28 AM
Decomp's on 500's are for pussy's

It is spelled "pussies". LOL :lol:

06-26-2006, 02:33 PM
Now what about the Accustart that Louis Mielke has on his 500? Whats the difference between that and a decompression lever? 500s are not hard to start even for someone my age and weight.Its just when raising the compression on this beast well everything suddenly becomes harder.

06-26-2006, 03:04 PM
when you port your top end.. just make 2 or 3 small grooves in the cylinder wall, just above your exhaust port. Make them about 1/16 deep, and 3/8 tall, starting in your exhaust port, getting less and less deep the more you go. Dont make them to big, only 3/8 or so long to the very top tip. This will let pressure escape when cranking, but will not effect your compression when its running.
thats the cheapest, easiest way to gain a little leverage when trying to start big bore beasts with high compression.

Louis Mielke
06-26-2006, 05:41 PM
The accu-start IS a decompression system. I'm also using a yamaha blaster kicker on my 500 which is much shorter than the stock one. Shorter kicker + decompress makes sense if you ask me.

Further more I would watch what you say is for pussies. There's a fine line between being stupid and being a sissy, you wanna wear yourself out kicking your 500 for 10mins when it finally decides to be a pig on you thats fine, I on the other hand like how its fairly effortless to kick my bike. If i need ot kick it 20 times to get it to start I'm no more the worse for wear when it finally starts, and my engine cases will be in one peice too.

I will also add that idon't worry about "finding the sweet spot" I get on it and kick it and when its behaving its only 1-2 kicks to start. ONce my jettings dialed in better I'm sure it will be better yet.

06-26-2006, 08:47 PM
Decomp's on 500's are for pussy's

It is splelled "pussies". LOL :lol:
Same Diff But who really *Edited**Edited**Edited**Edited**Edited**Edited**E dited* Care's? i stand by my statement. ;)

06-26-2006, 11:07 PM
If you ride how I do you would care. Im about 130 pounds now and I am about 5 foot 10 tall and I am 15. Its not fun having to tell my friends I cant stop because I dont want to start my bike again lol. Its not truly it being hard to start but sometimes the *Edited**Edited**Edited**Edited**Edited**Edited**E dited* will kick back at me because it has a mind of its own. First time it did it to me I was wearing tennis shoes and it sprained my ankle. Shattered my friends ankle too. The newer cr500s such as 90 or 91 -01 have reduced compression and reduced power compared to the 80's 500s.

Also making those notches in the cylinder, it wont affect the engine life or power?

Billy Golightly
06-26-2006, 11:28 PM
I think everyone that says the CR500s are easy to start has only tried cranking the later ones. The 85-87 ones did not have the scallops like Chainsaw mentioned. THe later ones come with them from the factory. The earlier motors ARE a *Edited**Edited**Edited**Edited**Edited* to turn over. I dont see how people crank them while their still bikes.

06-26-2006, 11:32 PM
I forgot about the scallops on the newer cr500s. Is that the reason why they have reduced power compared to the older ones?

Billy Golightly
06-26-2006, 11:53 PM
That, different porting, different ignition advance and timing on the CDI boxes. I found that one out trying to swap newer style CR500 ignition onto my 85. Wouldn't work.

06-27-2006, 01:54 AM
My KTM 550 two stroke was impossible to start. I weigh 200 pounds and could barely move the kicker unless I was up on crate and jumped down at the right spot (just past TDC).

I am quite strong in the quads and hamstrings as I still lift heavy and regularly. True these open class bikes depending on the state of tune can be a nightmare.

Make sure you reeds are good. I reduced the compression on my bike and it made a huge difference. It also let the bike rev further.

I still am curious about raising the compression again with a stock head.

If you have a 500 or 550, you won't call anyone a pu$$y in regarding to decompression releases.

06-27-2006, 07:37 PM
the scallops make no performance difference... Big bore single cylinder drag racers have been doing it for years. Its either the scallops, the compression release kits, find a fat friend to start it, or use the ole dolly with car batteries and a kenworth starter :)
I wish I would of did the scallops last time I had my 500 top end off. I didnt do it, and recently broke my kicker lever, clutch cover, and damn near my foot when it slipped the keyway and tried to throw me over the handlebars.

07-02-2006, 09:49 PM
those scallops or indentures above the exhaust port do the job with no problem. my 85 500 did not have them and i could not crank it for nothing. my 91 had them. now when i added them to my 85 cr 500 there was a big difference when trying to start the bike. go cr500riders.com search for the topic {start release} and there are some picture there also...

jason 32
07-03-2006, 12:46 AM
hummm?? bullshit i have a 93 it is a bad mother fucker lololol
there is a spot to kick them -yea i have ruined tennies as well
jet it right -time it if you can and it should start easily
i had a old yamaha cylinder witha decompression valve so i know what your talkin about ,yea it would be nice if it was perfected
as for gouging your cylinder how the hell would that help,and not affect it when running????? --- c'mon guys get real
if it lets blow by past the rings its gonna do it while running

07-03-2006, 08:28 AM
well i'm sorry you feel that way but as i have no problem with my cr 500 cranking now finding that sweet spot refers to bring the piston to top dead center and kicking like crazy. honda started marking those marks, scallops or indentures in the cylinder for that reason. the older model did not have them. my bike cranks in 3 kicks. 2 with the choke on and 1 solid kick everytime and my compressions is still at 190 psi. when you get a chance go to cr500riders.com. search for start release in the General forum. if you want to trier yourself out before riding then go right ahead.