Just finished rebuilding a XR200R with my son and it started right up last night. We let it idle for ten minutes and turned it off.  Started it up a few more times and ran it in the driveway for several minutes at a time. The machine shop that did the cylinder and head said to let the bike idle for half and hour to seat the rings but it seems everywhere else they say not to do this. Read online that the best way to break in the motor was to not exceed half throttle and do several accelerations and deceleration's in a row. Got on the trail and rode it pretty easy and then all of a sudden my son hears a screeching sound and the bike just stops. We let the bike cool down and still cant kick it over. Have it sitting in the driveway with some MM oil sitting on the top of the piston. (new wiseco piston and rings in overbored cylinder) . Not sure what to do next. My son and I are real bummed out since we've spent a lot of time and money trying to do this right.   I'm tapped out money wise and he wants to give up riding all together. Maybe tomorrow will bring a new perspective and a solution to getting this back running.  Just venting in frustration I guess.

Edited by scotteroni, 29 April 2012 - 04:13 PM.

God man. That sucks.
How olds your son? It's a shame he wants to give it up. Im only 14 and wouldn't give it up for the world.
Let the oil sit on top of the piston for a little. And then kick it with the spark plug out. If that doesnt work, I'd tear it down again and see what went wrong.
Stupid question: did it have oil?

And maybe you got off easy. Maybe a ring isn't installed right and it got fried. Maybe thats all thats wrong.

Tommorrows a new day, my friend.

Before heading out to get a bite I put the bike in gear and pushed it front and back and the piston loosened up. I think I overheated the piston by pushing the process too hard. I'm not sure if we should just try restarting it and see if it's ok (maybe it would make it worse? ) or just take the head off to inspect the rings and cylinder. If it's not scored up too bad we may be able to get by with an auto parts store hone tool and new rings.

Edited by scotteroni, 29 April 2012 - 06:04 PM.

Do not ever let an air cooled engine sit standing still with the engine running for more than a few seconds (longer during warm up), temperature rise is quite quick with out air flow.

A  common reported seizure on these engines is a lack of oil to the cam bearings. Years ago a friend had a XR200 seize while idling during a warm up from lack of cam lube. So checking the cam bearings might be a first step before pulling the cylinder.

A few seconds? Come on man. I can let my 450 idle completely still for over 5 minutes before it gets too hot. Now I'm not saying you should idle forever, but you could let a little bike like an XR200 idle for a long time before heat would become a concern. 30 minutes? No, but easily a few minutes - longer when from cold.

A screeching sound would more than likely be a bearing somewhere inside the bike, as mentioned it's likely to be a cam bearing. What kind of oil did you use, and how much did you put in? I highly doubt you seized it from pushing the bike too hard during break in. I've seen XR200s and various other small air cooled bikes rebuilt, warmed up, then immediately ridden hard with no ill effects.

Edited by Lead Head, 29 April 2012 - 10:24 PM.

Lead Head,

   Is your 450 air-cooled?

[quote name='chuck4788]...Do not ever let an air cooled engine sit standing still with the engine running for more than a few seconds longer after warm up' date='..[/quote']

Edited by dirtbkr188, 30 April 2012 - 03:17 AM.

I filled the lubricating cell below the cam shaft with 30 wt and put moly paste on the cam lobes,cam bearings and wiped some MM oil on the cylinder before putting in the piston. I installed the rings with the writing on top and in the right piston cut out as the wiseco 1 and 2 ring thicknesses are different and you can't mess them up.  I also filled the motor with straight 30 wt  per instructions from the shop. This motor has a new cam chain and upper and lower cam sprockets as well as new chain tension spring, I made sure the motor was warmed up before heading out. I did notice after riding around for ten minutes doing the accel and decell process that when I stopped briefly to exchange rides with my son the bike idled down and stopped. I should of took that as a sign to let the bike cool down then. Thinking it was just a carburetor idle adjustment we restarted the bike and headed down the trail.  

My son was riding the bike when this happened and he said the sound from the motor before it stopped was similar to fan belt screech. Also he had stopped on the trail to talk to someone he knew while it idled for maybe 45 seconds before we took off down the trail at maybe 10mph on level ground before the motor stopped 15 seconds later. There was no loud clacking or rattling as if the top end was dry at any time during the ride. It was nice and quiet and idled perfectly.

We plan on taking the motor out and checking it out on the bench this week so I"ll give an update then.  Geez , there are as many opinions on engine break in as their are opinions on what oil to use. I should of erred on the side of caution and took it easy.

Edited by scotteroni, 30 April 2012 - 05:07 AM.

Lead Head, on 29 April 2012 - 10:23 PM, said:

Water cooling provides a large safety margin to heat build up for two reasons; it has a high heat mass and it takes a large amount of heat energy to boil.

I've observed the big temperature rises using a Vapor. On one ride in the summer while climbing switchbacks  in the mountains I monitored cylinder head temps on a XR and found that a short period of idling could run the temp above 400F.  I changed engine oil after that ride.

New engines are tight and air cooled engines don't have the cooling capacity of a water cooled engine and can easily overheat; the OP followed the commonly accepted practice of heat cycling to prevent the engine from overheating during initial breakin.

We just need to wait for the autopsy results.

I just went out and kicked over the bike and it started. It smoke quite a bit from what ever was left of the MM oil in the cylinder but cleared up to to pre seize level of light smoke. ( yes the valve seals were replaced with new honda valves ) I put a large fan on high in front of the bike while i let it idle at around 1200 rpms for around 10 minutes. I did notice that the motor does make a slight shushing sound  on the top end now.  Shut down the bike and did a compression test WOT on it hot and it read 200 psi. Let it cool down and I got a reading of 150. I just checked  and drained out the oil and the oil screen had a slurry of metal in it the constancy of saw dust mixed with oil . Just refilled it with Rotella 15-40 and ran it for a few minutes and took it down the street. Feels like the timings off. Maybe it skipped a tooth or something. Won't know until we take look at it this week.

Best not to run it anymore as it's just doing more damage.  A couple questions.  Did you take the oil pump apart and inspect it when you had the engine apart?  And did you pull the exhaust rocker cap to check oiling when you got it running? ( Always use a shop rag being careful not to burn yourself, or get oil on the exhaust when doing this check.)

As for all the opinions..........this is the internet, and anyone sitting behind a computer is suddenly a expert!

Old School Al

Yes I cleaned out the oil pump and replaced all the engine seals  and o rings during the rebuild. I did not take off the exhaust valve cover to check on top end oiling.  I did replace the o ring for the passage going to the head. I read some people leave them out. Three light green O-rings came with the Vesrah kit and there was enough space with the gasket to install one of them. I assumed the rest were spares since the manual did not show any others.
.

Rings when new are tight and create a lot of heat. Allowing the motor to idle and just come up to temp then shutting it down and cooling gives the rings a chance to break in and seat without overheating. We usally do three heat cycles and then ride it gently. This gets you close to your half hour of run time.
After just a half an hour of run time the motor makes far less heat and should not have any binding problems with the rings.

The motor has to come apart again.  Idling it was obviously a bad idea.

Live and learn right?

i"ve never heard someone say not to idle these before,  I idle my xr200 and xr400 and our honda farm atv's idled for hours at a time, and those have basically the same air cooled motor

I would check the cam sounds like the cam seized up I would not ride it until it's checked and verify the timing is still right

chuck4788, on 30 April 2012 - 08:09 AM, said:

But we're not talking about idling while climbing up switchbacks on a hot summer day; we're talking about a cold start to idle on a fairly cold spring New Hampshire day. If you're climbing switchbacks during the summer on an XR, your CHTs are probably already close to 300-350*F, it wouldn't take much to get it over 400. On cold days, I could let my XR idle for at least 2-3 minutes before the head even got near hot enough for me not to be able to touch it.


Anyways, back to the topic on hand: You mentioned that you put the rings in the correct lands, but did you verify ring-gap before installing them onto the piston? If the shop bored the cylinder a little on the small side, the ring gap may have been too tight, and once the engine got hot enough, the gap closed up and seized the piston.

Edited by Lead Head, 30 April 2012 - 12:43 PM.

MrBlahh, on 30 April 2012 - 12:04 PM, said:

I've had XRs since the early eighties and Idling never seemed an issue until I installed a Vapor on my 200 and discovered how high cylinder head temps could go.  I know from dyno testing that bad things start to happen to an air cooled motor after cylinder head temps get above 400F.  So since the overheat incident I keep an eye on temps and don't idle a hot XR engine. I also don't do fast idle warmups because if the head pipe can go red so can the exhaust valve.  That may be overreacting but those two changes in habit are not inconvenient and may help engine life.

Because of the overheat incident I also installed a XRsOnly oil dipstick temp gauge and have been pleasantly surprised to not see the high oil temps some say these engines achieve.

I agree that the cam sounds should be investigated.

was your 200 built up, high comp setup?

think of all those honda atv's with air cooled 125, 200, 250, 300, 400cc engines, we used ours for farm work and it idled for hours every week without melting down,  the TRX200 is a copy of the XR200,  same with the 250x and 400ex's

just not something I would worry about at all

I brought the piston, rings and cylinder to the machine shop and had the bore matched to them. He verified ring gap. The guy has a great reputation they build a lot of auto race engines many years now..  It was a Wiseco 66mm piston, new wiseco rings. Hes' a wiseco dealer and has done many installs of thier product.
I'm taking the motor out tonight and examining everything.  I'm determined to figure this out.

look for galling on the cam journals, if the cam seizes on these it will lock up the motor just like you described