rebuild intervals

[mountain thumper]

was just looking over some older posts and came across a scary post.
someone was saying how theyd ridden 50 hours without needing a rebuild.
my bike is apprx 30 hours old. im going to be seriously peeved if i have to dump another few hundred in it that often!!!
we had an old (and free) yami enduro, when we got it, cylinder was seized. poured motor oil into it, let it sit a week, got the little turd to pushstart! never did any other work to it other than replacing a crap-ton of levers, rode it for 2 years before i moved and got my first xr.
how often does a gg 2t need rebuilt? i barely ride mine, and when i do, i take it easy. i cant afford a rebuild a year!

 

[2 strokes 4 life]

Mine is a 2002 with well over 100 of hard hours and when i took it apart all it needed was a hone, cleaning power valve parts, and new rings. I think when i start racing next year i am going to put in a new piston that is slightly larger. In total with all new gaskets and what i listed it was only $150 at tops.

 

[JoshP]

How much riding is not that often? On my 98 I rebuild every year or 2 but I'm riding every Sunday, 1 night a week during summer and every Sunday all winter (only missed 4 weekends last year.). On my backup 97 I'm still sporting the original 97 piston and rings setup. Now this last year 07' I'm estimating around a little under 250 hrs on the top end (98) and it still looks good going into this season so I will hold out as long as possible. Continued carb cleaning will keep most crap from getting into the head and messing up your piston. I typically remove and clean the carb after 2 to 3 rides. During this I remove the reeds to check and inspect the whole assybly to the intake to verify no dirt is in there. Obviously this sucks to do but it way less cash (FREE) compared to a new top end. Take you front pipe off and check what shape you piston is in now and that should give you a good idea of how much time you have left on it.

 

[JoshP]

2StrokesForLife.
I love your bike photo of the old Yama. I still have my
79' IT 175 in the basement and take it out for a vintage
knee beating every once in a while.

 

[Eric K]

Keep your air filter clean and well oiled.

At 50:1 mix, I have gone as long as 120 hours between top end rebuilds with no ill effects other than moderately reduced compression.

I increased my oil in the pre-mix to 38:1. I get 90 - 100 hours with only 2-3 psi compression loss.

 

[2 strokes 4 life]

2StrokesForLife.
I love your bike photo of the old Yama. I still have my
79' IT 175 in the basement and take it out for a vintage
knee beating every once in a while.

Thanks man. The display pic is a 1981 IT465. I am in the process of rebuilding it into a hill climber. I will post pics of it next spring when i am done. The 175 also needs some work. Fun bikes for the age.

 

[skid jackson]

I pulled the top end off my 06 300 with about 60 hrs on it. All it needed was rings. Unfortunately I seemed to have some kind of mystery piston and could not get a set of rings to work with the original piston so ended up with new piston also. In fact the jug had so little wear that the first wiseco piston sent to me was too big for the jug ... even tho that was the only piston wiseco made for 00 to 06 gassers. ended up using a piston for an 04 gasser. A buddy of mine said ... do a compression check ...if it is good go ride!! I think thats going to be my approach in the future. I'm not rev happy tho and ride slow tight woods

 

[ricegas]

My 99EC300 still has stock piston and rings...never felt the need to pop the cherry on the topend yet. I don't ride every weekend, but usually 1-2 times a month if work and family allow time. I've been careful about air filter maintenance and trans oil changes, airfilter changed every ride and oil every couple. Run the bike 40-1 with-don't laugh-Honda HP2 and have never had a fouled plug or jetting issues. It runs like a top still, just as strong as my buddies "new" 05 ec300.

 

[mountain thumper]

i got a bunch of dirt in the pipe during a rollover, so i took off the pipe and silencer, the piston looks ok, and what i could see of the rings was good. looks like the piston has some kind of friction coating thats worn under the port.

 

[stay_upright]

I asked my local dealer how often i should replace the rings on my 05 300 and he said never! I checked compression at 150psi which seemed low compared to my KTM 200. I changed the rings (first time for the bike I think) and compression was 150psi tells me my dealer was right - no noticeable wear. I used to change piston and rings once per year on my KTM 200.

Buy a compression tester - measure compression now check every 3 months if it drops off 10-20psi and you feel like you want more power change the rings.

 

[Loosenut]

Stay_Upright, as long as GasGas is using standard materials for rings, pistons and bearings, you might want to rethink what your dealer said about never replacing your rings. They wear like any other ring.

 

[stay_upright]

I always prefer to try and take a scientific stance on things. My KTM 200 showed that compression was a very good indicator of ring wear and performance and hence I would rebuild on the basis of compressions tests. From removed worn rings the wear (structurally) was very small and hence the chance of breaking rings seemed negligable additionally I never heard of anyone breaking rings. Additionally I had used pistons measured and they had no wear measurable with a 3 point guage.

I use the same system on my Gas Gas - and with a couple of years use there is no noticeable drop in performance of compression. As I said I replaced the rings shortly after I got the bike but did not need to - there was no difference in compression and hence no noticeable ring wear.

I dont know what materials GG use for their rings so can't comment but would expect the bigger bikes (250,300) rings to wear a lot slower than the smaller bikes (125, 200) as generally the motor is turning over much slower. Also without a compression guage the average rider is a lot less likely to notice a loss of power from a 300 than a 125.

 

[JoshP]

I always go off the amount of hours on the engine. Even if it looks good I do a rebuild because it guarantees me a solid engine for riding and I'm not going to leave myself in the woods because I was pushing my luck a little too much.
Not to say you are pushing your luck, but a small amount spent on preventive maintenance is a large investment in the long run.

 

[GMP]

What you also have to consider is pistons fatigue in the skirt area. It can look good but be a time bomb if it has a lot of hours on it. Top end kit is relatively cheap, I don't even waste time doing rings only. Like Josh I cut no corners and have no worries.

 

[blitz11]

GMP has made this point before, but you can't measure fatigue.

You can design steel components to have an infinite fatigue life...generally that stress level is just a bit less than the steel's ultimate strength. Unfortunately, steel is the only common metal with that property. If you don't exceed the infinite fatigue limit stress, your part will last forever (discounting, of course, corrosion, nicks and other stress risers, etc.)

Aluminum, however, does not have that property. With aluminum, you accumulate fatigue cycles, and eventually that part is going to break. You can't get around it.

It seems to me that people who avoid doing top-ends are in some sort of denial. If you need to rely on your machine, and these bikes are race machines, you really need to do the maintenance. If you don't ride it hard, use low revs and not much throttle opening, you're not stressing the top end much, and maybe 100-150 hours between top ends is ok. If you're racing it, high revs, big throttle opening, then $200 for a top end every 40-50 hours isn't much to ask.

Ask my coworker who broke a piston skirt, skirt pieces wedged between crank and crankcase, cracked a case, and just spent $800 on parts and a cylinder replate, called in favors to get the case welded, and 8 hours of my time to get the bike back together. Had he replaced the piston regularly, he could have ridden a lot more, and saved a bunch of money. He's now back to where he was had he done his maintenance properly.

blitz

 

[blitz11]

oops. infinite fatigue strength for steel is about 1/2 of its ultimate strength. sorry.

 

[Loosenut]

Having had a piston skirt bust on my '91 CR250, I don't push my luck.