So This Is What My Cr 125 Is Doing

[crazy3rdgen]

Making a tick noise on the top end. It wasn't this bad when I bought it but slowly getting worse so I stopped riding it. I've notice that the power band is coming in late and some times not at all. Awhile ago I went to start the bike and I had to bump start it, a lot of oil spooged out, hasn't done it lately. But I did a compression test on it today, 110psi ! The compression was getting worse, now it is barely able to start when kicking, now you gotta bump start it. So it's sitting now till I have time to fix it. What should I get to fix these problems/what could it be? Should I get a manual for my bike it's a 98.


Thanks for your time : )

 

[Flygirl]

I am no means an expert on this but I had the similar problem and it ended up being the power valve which as I understand affected the power band. We ended up replacing the piston as well. Best of Luck!

 

[John Cena]

I'm no expert either but 110 PSi is low, Sounds like your pistons worn out and is slapping in the cylinder. About $120 for new pistons and gaskets.

 

[crazy3rdgen]

yeah I hear it's supposed to be around 180-200?

 

[j32]

buy a book, you will not regret it ,even if it is just too change the oil

 

[QKENUF4U]

buy a manual
buy new piston/rings/gasket kit
pull bike apart
have cylinder checked for bad scratches etc. (fix accordingly)
put back together
ride

 

[scott robinson]

a manual is the best thing you will ever buy for your bike you will save lots of cashl

 

[crrod]

yeah I hear it's supposed to be around 180-200?

It would be nice if the manufacturers would give some sort of idea for compression. I was talking to a guy tonight that races bikes, he has switched to 4 strokes, but used to run 2 strokes. It is a family of 5 (dad and 4 sons) so they had several bikes for reference, and several rebuilds for reference. He was saying 160-180 was about normal for a brand new top end, and once broke in they generally ran between 120 and 160 psi. He said they would usually run them until they got down to 90 to 100 psi, then they would send the cylinder to a place in New York for a hone and replate, plus get the piston and rings from the same place. I'm only mentioning this as a reference since the factory's will not give a point of reference and it is anyone's guess.

My 99 CR125 has 120 PSI, and hangs with a couple of newer YZ125 with new top ends. Generally starts first or second kicks, and it does have "ticking" sound in the engine, slightly louder than the two YZ125's with new top ends. I've been told this is due to the aluminum frame aplifying the sound. It is mostly evident around idle.

I do have a more consistent power band performance since I removed the exhaust valves and clean what carbon was on them, off. I plan to put in a wiseco piston, ring, pin, and upper bearingin the near future though.

 

[crazy3rdgen]

hey, I know the ticking you're talking about but this was getting louder and louder as I continued to ride it. So I pulled the motor and the head/the casting (cl wall thing : ) And the cl walls look to be in great shape not needing a hone at all. I checked for play in the crank , ( up and down ) there is no play besides a tad side to side and same for the piston. However the top of the piston looks pretty burnt up and the ring is obviously shot. I'm gunna go ahead and buy a manual and see what all I can do to make sure I get this bike running at full potential without hurting my wallet. Any suggestions on what to do? What all to check? How I know what needs to be rebuilt? Thank you

 

[crrod]

I'm still debating. I do a search on this forum, and all that does is muddy the situation. My thought is whether to use a Wiseco piston kit or go with OEM parts. If OEM, I'm finding multiple part numbers for my bike that has the "A" cylinder. With Wiseco, there is no A, or B.

I can actually get the OEM stuff a tad cheaper than I can Wiseco (OEM coming from oem.honda-factoryparts.com and Wiseco figured at RockymountainATV).

I am leaning towards the wiseco kit, and adding piston pin bearing (I figure cheap insurance). I already have the cometic top end gasket set. I am also leaning towards the Boyesen Pro Stock Carbon Fiber reads for 38 bucks. My 99 CR125 appears to be un touched other than a FMF fatty and Shorty silencer. The jetting, needle and air screw where still at the facotry settings, which were way different than what FMF recommended for this bike with their pipe. I lowered the needle, but haven't changed the jetting. I give it a good ride last night and then pulled the plug. The plug, with the lowered needle, looks awesome, it was quite a bit dryer and was actually brown as oppsed to usually wet and black. I also tested compression again after a good ride and after I had de-carboned the exhaust valves (which weren't that bad), and I am still at 120 PSI.

just looking throught the exhaust port, my piston and cylinder looked great. I am planning to just have my local machine shop run a ball hone down the cylinder to clean it as recommended and then simply install a standard piston and ring. Once that is done, I may play with the jetting and go back to the OEM plug which is a BR9EG (I am currently running a B8ES with great success, I fouled the original plug the first time I tried to start the bike and replaced that plug. Beend running on the same plug for over 6 hours of riding now with mostly first kick starts).