160lb compression on my EC 300

[HydroDog]

I've been following this thread for a while to see if I could help out. I just went out and check my compression for shi$ts and giggles with the bike cold at 40deg. with the throttle wide open I got 170 psi. on my craftsman tester.

[FFRDave]

I could remove the head and run the piston to the bottom of its stroke and look for damage to the cylinder wall, or maybe alluminum deposited there. I could also take the pipe off and check the front of the piston.

Besides that, I really dont know what I would be looking for.

I really dont want to remove the cylinder again. I have F'd that part up so many times, that my confidence is just shot. Part of what is going on here is that I have had so much trouble, that I utterly lack confidence in my own work. PEB was right earlier when he told me to just go riding and I will know in a couple hundred hours.

I will continue to check the compression before each ride and look for a decline to tell me if I might be having trouble.

[PEB]

Dave, You can see alot with the pipe off, nearly the whole back part of the bore. If you are going to go to the trouble of taking the head off take the whole jug off. I hate to say it but if it siezed you should tear it down before something else happens. A replate or new piston is chump change compared with replacing bottom end parts. Besides now is the time of year to deal with this s%^t. It could run great for years or it could sieze on you again fourty miles from the truck this summer. Several summers ago my 02 ate a tranny deep in the Manastash system and the truck was near Cle-elum. It took about six hours of cursing, pushing, pulling, crashing, and towing with a wr450 to get it back to the truck. I hate to be a buzz kill but I think you should tear it down.

Paul B

[GMP]

For starters, pull the pipe and reed block, that will show you the front and rear of the piston. Better yet, just pull it apart and take some nice photos.

[PEB]

Any update? Don't give up on your GG you will get it sorted out.

Paul B

[FFRDave]

In a week or two I plan to send my head off to RB Designs for a squsih-band adjustment, and that will give me the look inside that I need, and I will take compression measurements at that time too.

The bike seems to be running just fine.

I decided to stop worrieng and just go have some fun. that is what these machines are made for.

[FFRDave]

Its all good.

I think Ron at RBD could definatly do some magic with my 300 head squish-band. However, I think its running just fine.

I took it for a three hour ride at the local hill area and just rode and had fun, and then another ride in the sand dunes. After all of this riding I did another compression test. This time I got 165 lb. on three separate tries, each with 4 0r 5 kicks at wide open therottle (as previously suggested). The results were consistant and well within my expectations. Heck, its even a slight improvement over the previous result of 160 lb..

I did a leak-down test too and she held 165 for 10 min with no signs of leakage. After 10 min. I was satasfied that it was just fine.

[rrguy]

I think the compression test is a good maint tool to check engine condition. If you would let us know what you read when you get the head back, that would be appreciated. I will do the same.

Not sure how gentle of a break in you did, or what prep you did to the cylinder while it was apart, but my guess is the ring had not completely broke in. the comp may improve even more? It seems with the plated cylinders & harder rings it takes more to break them in. Or in another words a proper but not too gentle of breakin procedure. I remember reading some street bike long term reviews & they actually made more power after 20,000 miles etc..

thanks

[101racing]

Always remember that a compression test will vary from different altitudes,same bike. We live in MT and start out at 3700 ASL and go up. The 300 KTMs can be down in the 150lbs stock. Most of the time just playing with the base gaskets swap outs and getting that piston a little closer to the top will give another 15 lbs. Lowers port timing a little for some more low end. JMHO