2 Stroke 1998 CR80R

[Trfsrfr]

I just picked up a 1998 CR80R.
Got it for next to nothing, a complete bike, non-running.
1 - Does anyone have a download for a factory service manual?
2 - Bike has no spark. Tried 2 other coils with no luck.
3 - Compression is 134psi with carb on.

Looking to get this going for my boy ASAP...
Any help is much appreciated, as always.

Thanks!

 

[Mihylo33]

I just picked up a 1998 CR80R.
Got it for next to nothing, a complete bike, non-running.
1 - Does anyone have a download for a factory service manual?
2 - Bike has no spark. Tried 2 other coils with no luck.
3 - Compression is 134psi with carb on.

Looking to get this going for my boy ASAP...
Any help is much appreciated, as always.

Thanks!

Start with the magneto break the bolts loose and clean the contact points. Do the same to the coil. Still no spark disconnect the kill switch. Replace the plug cap chase bare wires.
This little bugger should start with a well cleaned carb and fresh premix.

 

[Trfsrfr]

We didn't get into it much but we did disconnect the kill switch, tried 3 different plugs, the above-mentioned coils, and checked the wiring.
I am not sure what the compression should be cuz I dont have a manual, but I watched a short Youtube video of a kid kicking an 01 and he had 170 psi, so I assume I need to rip the cylinder off.
Piston is clean with some slight scratching on the sides.

Overall the bike is in decent shape; needs tires and some plastic, but otherwise good. It has a really nice, full FMF exhaust, and ASV clutch and brake handles, so I assume someone loved it at some point.

The only place I have found a manual for this is here;
https://www.tradebit.com/filedetail.php/278935672-cr80r-cr85r-service-manual-repair-1995-2007
I have never heard of this site before and they want $8.00 for the download.
Anybody have an alternative?

 

[Trfsrfr]

After using some sandpaper on the coil mounting bolts I now have some spark.
It's not a very bright spark so I am not sure if maybe it was there before and we just couldn't see it, or if the sandpaper helped, but it still wont fire.
I downloaded that manual I linked to above and it's very nice, but it doesn't say what the compression psi should be.
Anybody know what that number should be?

Gonna remove the carb and go through it.

 

[2strokesteve89]

After using some sandpaper on the coil mounting bolts I now have some spark.
It's not a very bright spark so I am not sure if maybe it was there before and we just couldn't see it, or if the sandpaper helped, but it still wont fire.
I downloaded that manual I linked to above and it's very nice, but it doesn't say what the compression psi should be.
Anybody know what that number should be?

Gonna remove the carb and go through it.

The compression ratio for that bike was 8.4:1 to figure what compression psi should be, the calculation is atmospheric pressure multiplied by the first number in the ratio then divided by the last number. So in your case if you are at sea level, 14.7 X 8.4 = 123.48 / 1 = 123.48. For your convenience here is a atmospheric pressure chart.......



There are also the consideration of ambient air temperature, but this formula should get you close enough to get a good idea if the top end is worn out or not.

 

[Trfsrfr]

Hey thats cool. Thanks Steve!
So if I'm at approx 1200ft msl, then that would be roughly 14.1 x 8.4 = 118.44.
Not sure how much difference it makes, but when I checked the compression it had the carb on, and throttle was closed, and it came out to 134psi...

 

[2strokesteve89]

Hey thats cool. Thanks Steve!
So if I'm at approx 1200ft msl, then that would be roughly 14.1 x 8.4 = 118.44.
Not sure how much difference it makes, but when I checked the compression it had the carb on, and throttle was closed, and it came out to 134psi...

Like I said temperature makes a difference, as does carbon build up in the head and top of the piston. Also is your tester gauge accurate? But I would say compression isn't an issue here.

Edit.....for a good test its best to have a warmed up engine (if possible) and hold throttle open while kicking engine over 5-7 times.

 

[Mihylo33]

After using some sandpaper on the coil mounting bolts I now have some spark.
It's not a very bright spark so I am not sure if maybe it was there before and we just couldn't see it, or if the sandpaper helped, but it still wont fire.
I downloaded that manual I linked to above and it's very nice, but it doesn't say what the compression psi should be.
Anybody know what that number should be?

Gonna remove the carb and go through it.

You'll have to go through and hit all the ground contact points like I said before. Cut a 1/2" off the plug wire and reinstall the cap. Clean the carb twice and then once more for good measure. It will run today if you go through it properly and carefully.

 

[Trfsrfr]

Also is your tester gauge accurate?

Yes, it's a good gauge. Had it for many years.

.for a good test its best to have a warmed up engine (if possible) and hold throttle open while kicking engine over 5-7 times

The engine wont be warm, but I will retest today after I clean the carb.

Cut a 1/2" off the plug wire and reinstall the cap.

Do you mean remove the plug boot and strip 1/2" off the wire itself, then reinstall the boot?

 

[Mihylo33]

Yes, it's a good gauge. Had it for many years.


The engine wont be warm, but I will retest today after I clean the carb.

Do you mean remove the plug boot and strip 1/2" off the wire itself, then reinstall the boot?

Yes. But just cut the wire short don't strip it. There's a prong in the boot that inserts into the wire.

 

[ossagp]

The compression ratio for that bike was 8.4:1 to figure what compression psi should be, the calculation is atmospheric pressure multiplied by the first number in the ratio then divided by the last number. So in your case if you are at sea level, 14.7 X 8.4 = 123.48 / 1 = 123.48. For your convenience here is a atmospheric pressure chart.......

View attachment 30189

There are also the consideration of ambient air temperature, but this formula should get you close enough to get a good idea if the top end is worn out or not.

If you can get within 5% of that calculated number in a single reveloution I would be onboard with that method. I don't put a whole lot of faith in compression tests, especially on two strokes. A well used yz85 kicks out a solid 159 on my gauge in three kicks. Probably 40 hours on it play riddend, anything from lugged to screamed down the access road at Sutton.

Get 140 with one good solid kick and I would say it's new.

134 in 5-7 kicks, I would say that ring, piston, cylinder are in line for replacement soon, but should start and run. my yz 125 with the 139 kit and relieved power valve is on the sluggish side in the 150's.

 

[ossagp]

After using some sandpaper on the coil mounting bolts I now have some spark.
It's not a very bright spark so I am not sure if maybe it was there before and we just couldn't see it, or if the sandpaper helped, but it still wont fire.
I downloaded that manual I linked to above and it's very nice, but it doesn't say what the compression psi should be.
Anybody know what that number should be?

Gonna remove the carb and go through it.

if you can get spark at all, it is going to run from my experience. push it in gear with the plug grounded and i bet you get a much brighter spark.

 

[Trfsrfr]

Okay, got the carb off and cleaning it, reeds appear to be in fine shape, no chips, and sealing properly.
Compression on 1st kick - 86 psi
7 kicks - 134 psi
Took the whizzer wheel to the grounds on the coil mounting bolts and they're bare metal now.
Also tested the coil, exciter and pulse generator resistance, all came within spec. I do not have a peak voltage adapter though so couldn't test that.
Gonna tackle the plug wire next.

I did not remove the flywheel cuz I dont have the universal holder tool to tighten that nut back up, but I did loosen and re-tighten the exciter mounting bolts, but they were good.
Gotta run to Ace hardware to get some new carb bowl screws as well...

if you can get spark at all, it is going to run from my experience.

Perfect, thats what I want to hear.
I just want to hear it run and let the boy ride it a bit before I install a new top end. Plus I just started work again so I gotta catch up from X-mas and get some $$$ coming in, so maybe in a few weeks will we do the top end.

 

[2strokesteve89]

If you can get within 5% of that calculated number in a single reveloution I would be onboard with that method. I don't put a whole lot of faith in compression tests, especially on two strokes. A well used yz85 kicks out a solid 159 on my gauge in three kicks. Probably 40 hours on it play riddend, anything from lugged to screamed down the access road at Sutton.

Get 140 with one good solid kick and I would say it's new.

134 in 5-7 kicks, I would say that ring, piston, cylinder are in line for replacement soon, but should start and run. my yz 125 with the 139 kit and relieved power valve is on the sluggish side in the 150's.

Depending on what year that YZ is it would be hard to compare readings, a 2005 YZ is at 12.3:1 which would put that one at 180 psi at sea level, my post was simply illustrating how to get an idea of what a healthy reading should be. I agree it's not a exact science but it gives a good baseline to go by.

 

[Trfsrfr]

my post was simply illustrating how to get an idea of what a healthy reading should be. I agree it's not a exact science but it gives a good baseline to go by.

I appreciate all the responses. I'm going to fire it up and ride it and see how it feels. I doubt it will be any slower than the kiddo's XR100 so I am sure he will be happy no matter what the compression reads

And if it hits the powerband and runs well, I will be happy with the $200.00 I spent on it.