1997 Honda XR600R questions

Hey y'all I'm brand new to Thumper Talk but have been reading very helpful posts on here for a while now so I decided to join.

I recently bought a 1997 xr600 for $600. It was a steal. The lady who I bought it from was selling all of her husband's old stuff because he had passed. I didn't really care if I bought into a money pit cause I wanted to take on the project.

It ran great when I first got it. I changed the oil and the spark plug. But it didn't need much more than that done right from the start. It recently started smoking pretty bad when I ride it. And the past few times I've ridden it would rev really high then really low over and over again as I was holding the throttle steady and cruising in 3rd gear. If I let off the throttle to downshift, the motor would die. It would start back up fine and idle fine until I started riding again, then it would start revving high and low again. I got tired of messing with it, so I let it sit for a few days. Yesterday I started it up and there was a huge cloud of smoke right off the bat and it continued until I shut the bike off. I'm thinking it's a combination of the carb and maybe the top end needs to be rebuilt. But does anyone know what it could be? Any help or input at all would be very helpful!

Much appreciated,


Is it blue smoke or black? Did she say how long the bike sat since he passed and you bought it? If it's blue smoke it could be rust had done some pitting in stuff like the cylinder and it is now allowing oil to pass by. The high and low running sounds fuel related if the motor doesn't sound like it is seizing.

I'd take the carb off first and really clean it, quite likely dried up fuel is blocking passages. Look inside the gas tank and see if there is a bunch of dirt or rust that may be clogging the petcock filters.

Edited by jjktmrider

It had been sitting for 6 months without being started before I bought it.

It is a blueish/white smoke. And it does smell like it probably oil burning off.

I will do that. I appreciate the reply.

Maybe put some Marvel Mystery oil in it and run it mildly for a bit. Maybe some seals got a bit dried up or the rings need to "reseal" if that even can happen. If it is smoking from oil due to sitting, other than running it to see if it clears, not much to do unless it is torn down. Either rings or valve seals have gone bad then. A mild fix job compared to it knocking and have a bunch of shot parts. Always a possibility it did that when the other guy ran it.

Ok. How would I go about checking the valve seals or rings? I'm not super experienced with this. But I'm trying to learn everything I need to know. Again, I really appreciate the help.

A compression check would give an indication of how the rings are or if the valves are sealing, but theres another test for that if poor compression is found. The valve seals no real way to check them other than replacing, they generally have a sign when they leak which is puffing smoke when you first start the bike. They wouldn't cause the up/ down rpm your getting.

Does the motor make any kind of noise? They normal have a whine, maybe a faint clatter but not real loud or distinct.

Just how much have you run it since buying it? have you run it for a decent trip to get it nice and warm?

Take the spark plug out and tell us what it looks like.

Edited by jjktmrider

How do I check the compression?

There is definitely a big puff of smoke right when it starts up. Then the smoke dies off for a second and then comes back steadily. I don't notice any abnormal noise while the motor is running. But it does seem to have a bit of a whine to it, nothing extreme though.

I have gotten out an ridden it quite a bit on some trails since purchasing it. But I haven't ridden much since the smoking started. And haven't ridden at all since the up/down rpm tantrum happened. The spark plug was in great condition. Looked almost as new as when I replaced it.

One thing is to make sure you didn't overfill the bike with oil, check the level on the dipstick a couple minutes after you shut it off from running about 5 minutes. Should then be at the full line. The motor sounds like it is in good condition if it has that mild whine and no ticking/knocking, so that's good.


It may be that you have 2 separate things going on. The puff of smoke and sometimes constant smoke definitely screams valve seals. To replace them is easy but requires the head to be taken off , not sure if one can get the valve springs compressed with the head still on the motor by pressurizing the cylinder with an air hose. If it is possible, the seals can be fixed without removing the head. You would need a valve spring compressing tool.


If you keep a very close eye on the oil level and never run it low on oil you can just keep using the bike with the seals leaking, it just increases the odds that you'll run out and do damage to the cam and rockers. If it just keeps billowing smoke, then it's definitely time to fix.


The rpm up/down sounds a lot like a fuel issue. maybe drain all the gas out of the tank using the petcock and run a hose down into a gas can. You can then watch  the flow and see if it slows/stops sometimes. Then refill with a good quality gas, I use 91 octane premium, no ethanol, some of these bikes were made before ethanol was added to some gas grades and it can cause issues with rubber and seals in the carb(not the valve seals). Don't know if the '97 is that way or not.

Take the bike for a spin and get it doing that rpm varying issue, then slowly turn the choke on to see if the problem get better or worse, I predict worse, but ... that will tell you quite a bit on what is going on.


Spray  the intake boot (between carb and motor)with wd-40 as the motor is running to see if it changes . If the rpm suddenly goes up or down as you spray an area on the boot, then it's an air leak. Otherwise take the carb off and disassemble and clean everything out good. Take a few closeup pics of things as you take apart so you can go back and see how things were if your not familiar with things. Go slow and study how it is, there isn't a whole lot of parts but each one does make quite a difference if not installed or put in wrong.


To check compression, you need a compression guage and the hose gets screwed into the spark plug hole. Then you open the throttle full and kick it over 5-8 times and read the guage, it'll say how much pressure is being created by the piston. Should be 130-150psi minimum.

Ok my oil level is good. I took the carb off, disassembled it and cleaned it really well. I put it back on and since I already had the tank off I decided to check the petcock. I drained all the fuel and as it was going through the petcock it definitely seemed to stop and go repeatedly. I took the petcock off and the internal fuel filter on the petcock was completely eroded. The pieces of the filter were clogging the fuel to the petcock. I cleaned it off real good and the filter was so brittle it just broke to the touch. Now my question is: is it worth it to pay the $60 to buy another one? Or do I really need the internal filter when I have an in-line filter?

Now with the smoke, I think you're exactly right. Since my oil levels are good I think it's definitely valve seals from what everyone has been telling me and what I've been reading. Someone also said my valve guides probly need to be replaced? I have no idea how to replace either the valve guides or valve seals. Do you know of any good videos I could watch to get an idea of what I will need to do? I don't want to mess around with riding the bike like it is because the smoke is so bad. I would much rather just replace them.

Thanks for your help!

To replace the valve seals you unfortunately need to take the head off the motor. It requires a valve spring compression tool to compress the springs and remove the keeper. The seals are right there under the springs.

It is possible to hook an air hose up to the sparkplug hole and pressurize the cylinder, then push down the spring plate to remove the keepers without removing the head, but it is tricky and you can't allow the air to cut out because then the valve will drop into the cylinder.

Don't need to worry about the guides, I doubt they are worn out yet. To replace them requires the head to be taken to a motor shop to completely regrind the seats afterward to make sure everything is inline. Basically a complete head rebuild. The motor is nice a quiet so I wouldn't waste the cash this time, just replace the seals.

As far as a video, I don't know of one but I bet a search on youtube would result in a few, even a video of an XT600, KLR600/650, DR600/650 head work is the same process and steps across the board. Just make sure to get XR600 torque specs on all bolts when reassembling. Get a good seal set either OEM Honda valve seals or a good name brand Viton, not those cheap sets on ebay.

I would get one of the replacement petcocks off ebay for around $30, there are some decent ones, don't get the china made ones, otherwise a used one from ebay will work also as long as you get one off a newer bike. XT , DR, NX, XR-l and many others use the same petcock. Just verify mount hole spacing and outlet placement are the same as what you need. The filter in the tank is nice because it will stop the petcock from getting plugged from junk in the tank, otherwise with a good inline filter it isn't a necessity.

Edited by jjktmrider

Awesome. You have been a really big help. I really appreciate it. I will let you know how the valve seals turn out. Thanks so much!

Alright..so I cleaned the carb really good and got it put back on the bike. I attached all the fuel lines and everything and put some fresh gas in it. Tried to start it up....nothing. It doesn't even sound like it's trying to turn over. The fuel is flowing out of the petcock good. Is there something I'm missing or could've done wrong?? It's like there's no fuel getting into the motor.

Open the drain screw on the bottom of the carb bowl to see if there's fuel in the carb, just in case the needle valves been pinched shut. If fuel comes out, try putting a a teaspoon or 2 of fuel(with a drop or two of 2cycle oil mixed) down the sparkplug hole. If should fire at least and that will tell you that the carb wasn't put back together quite right.

I opened the drain screw and the float bowl was completely dry. I found out that the float was off and it was causing the float valve to block the fuel even if there wasn't and fuel in the float bowl. A quick adjustment and she started right up. Runs like a charm now. Still have to replace the valve seals and plan on doing that within the next few days.

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