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XR80R top end rebuild?

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Now that I have the bike running consistently with the CDI upgrade, it's time to rebuild the top end. It's smoking a bit while riding.

 

It's an 86 XR80R. I've found this kit from Wiseco, http://www.ebay.com/itm/111493071617?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

What I don't know is if this kit is higher compression over stock. Anybody use this kit and have any in site? I don't mind if it does, but I'm not looking to pump this motor up a lot. Maybe just a bit.

I'm planning on a new cam chain if I can change it without splitting the cases, but if I have to that's not that big of a deal either.

 

Any suggestions or recommendations for this rebuild would greatly be appreciated. If I can increase power just a bit without getting carried away it would be nice.

 

Also, is there a descent exhaust replacement over the OEM pipe that won't break the bank?

 

My sons getting pretty tall, so I don't think he'll be riding this much more than a year or so. But I want this bike in good shape for when he outgrows it and I sell it.

 

Larry

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I can't speak for the piston kit but I would definitely get an xr100 carb. It is near impossible to find jets for the xr80 carb which u will need after mods.

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I got hold of the seller and was told this piston is at the stock 9.7to1 ratio. So I ordered it along with a new cam chain.

 

Not sure how much more to look for at this point to do a mild upgrade. Just the piston itself probably won't do much more than bring it back to stock specs.

If I can get a recommendation on a better exhaust I might be tempted to do that too.

 

We'll see where that goes as for the XR100 carb.

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With 151 views I'm having a hard time believing nobody has replied with and suggestions.

 

I have a parts list set up to order all the parts from Honda including a new cam and rockers to split the case so I can replace the cam chain. The Motor is out with the cylinder off just to find out there had been water in there from the PO probably leaving it out in the rain with no carb on it. Water sat in there long enough to pit and rust the cylinder and ruin the compression sealing.

 

But I'm kinda interested in pumping up the power just a bit with this rebuild. Is there an aftermarket cam that will increase power without having to do a bunch more mods other than exhaust and carb? I'm not looking to make a race motor, just increase the power a bit after I have the cylinder bored 1mm over.

 

Come on, I'm sure someone out there has done some upgrade mods to one of these models that's helped make it more fun to ride! Give me some suggestions to consider, please.

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Saturday my son pulled the motor from the bike and took the top end off all by himself. When it was apart it was apparent why it had been smoking.

The previous owner must have had this sitting outside for a long time with the carb off it and the rain got into the cylinder and rusted it pretty bad as you can see in the picture. I remember when I got this bike I had to buy a used carb because it was full of water corrosion. I must have ignored the cylinder just to get it running. That was 5 years ago.

 

Since I haven't gotten a response here about a better cam, I've ordered all the gaskets and seals from Honda including a new cam, rocker arms, cam sprocket and chain tensioner. All of it should be here in a few days and only cost me $230 total. I received the Wisco piston kit and chain today. Tomorrow I'll need to contact the machine shop to get the cylinder to them and get it bored out. I just hope it doesn't take him long to get it done. When I get the parts from Honda I'll split the cases and change out the cam chain. No need to have it apart till they get here. Little things can get lost don't ya know!

 

While I wait I'll pull the valves from the head and do a little port work to clean them up a bit. In my opinion that's just a free way to increase a little more power.

 

DSC_1300_zpsiikfj6zc.jpg

 

The piston kit and chain.

DSC_1299_zps8ljszva5.jpg

 

And finally, the damage that was caused to the cylinder by water sitting in it for a long time. You can see the rust line while it sat on the kickstand for a long time.

DSC_1302_zpsxujhrqsj.jpg

 

 

With as bad as this was I'm sure the compression was pretty low. With the rebuild it will probably have quit a bit better power and be more fun for him to ride.

Updates as I go along IF your interested.

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I have a question. On the bottom side of the stock exhaust silencer there's a block off plate that covers a rectangular hole.

What is the intended use of this? Is it to increase flow that will increase a bit of power?

DSC_1303_zpsvgmsrlxp.jpg

 

DSC_1304_zpszsuyxcaa.jpg

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Hopefully by X-mas my new pistons will be done. 92cc bore-in and can have from 10-12 compression. Cams I would have had your old cam redone at WEB and probably had a #68 grind on it done. Yes on 100 carb upgrade. Many places have a good pipe for these. Yes on doing some porting on head

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Thank you for the info. I'm going to wait on a cam till my son builds up his riding skills. I can always change it later.

 

On the 100 carb, what years are the recommended. If I'm correct, I need to get the intake boot also right?

 

Are any of these new carbs suitable? I see brand name carbs which would indicate there not aftermarket junk.

http://www.ebay.com/sch/i.html?_from=R40&_trksid=p2060353.m570.l1313.TR4.TRC2.A0.H0.Xxr100+carb.TRS0&_nkw=xr100+carb&_sacat=0

 

BTW, will the carb upgrade work well without doing a pipe or cam for now?

Edited by LRCXed

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Ask the xr100 experts. A PZ26 actually has approx same area as a 22mm smooth bore at least on brand I checked. Jet kit from 85-135 is available from Trail bikes for cheap. You should be able to dial it in pretty easy.

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The plate on the bottom of the exhaust silencer is a clean out plate. Common on many Honda air cooled bikes over the years. You can remove rust, carbon, water anything else that has accumulated over time. The bike is not designed to be used with the plate removed and no performance increase will happen. The stock camshaft is best for your son to learn on.

Edited by tlrmark

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Thanks for the info on the carb and the stock exhaust. With the lack of specific recommendations I'm going to just rebuild this and put the stock parts back on it. Changing carb and exhaust is easy enough after I get it done and break in the new cylinder.

 

I expected the parts to arrive from Honda today. But with it being Veterans Day that didn't happen. But last night I decided to split the cases and get things cleaned up and painted so I was ready when the parts arrived. After that was done I spent some time cleaning up the ports in the head as well as cleaning up the shrouds in the chamber around both valves. I was REALLY surprised at how far off center this casting was. As you can see, the casting is shifted so far to one side that there's only 1/8" sealing surface on one side of the intake port. I DID NOT open it up that far. You can see some of the casting line still in the port where it was before I started shaping the ports. It did take a bit to match port the intake runner to the head, but I'm sure it will help the overall flow.

 

All the internal gears, crank and clutch were in good shape and up to specs. So cleaning and prep and painting for reassembly was all that was needed.

DSC_1311_zpsxnwmlaxv.jpg

 

Porting all done, but this pic was before I re cut the valve seats and lapped in the valves.

DSC_1315_zpsy8moaaqd.jpg

 

This shows how far off center the casting is. The arrow points to the original casting marks in the port. I only ported it out to that line.

DSC_1316_zpscoayan3a.jpg

 

I put the case and side covers together, empty, and painted them with PJ1 satin case paint so they would be well cured before I started assembling the motor. I like it when the cases are painted and the new gaskets don't have paint over them. I think it shows more attention to detail. Hmmmm, this will get covered with mud and dirt won't it!!! Oh well, it looks good in the beginning!

DSC_1317_zpsd6ao8ktq.jpg

 

Hopefully all the part from Honda will be in tomorrow so I can assemble the lower end before the cylinder re bore is done. I'll update as things go along.

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Wish I would have seen this post earlier! I just finished doing a 2005 crf80f for my 10 year old 70 lbs. bought an old 94cc poweroll piston and rings on e bay had the cylinder bored 3.5mm and decked .020, ported cylinder head and lapped valves. Bike already had a pipe on it, and with a little tuning it really woke the the 80 up. Changed the sprockets to next taller ratio and he rode the hell out of the 80 for a few months. I then bought 2 used xr100 carburetors and worked on them and finally got one to work really well,if you do this mod you will need the xr100 intake and air box boot (fits in the 80 air box). bike really has lots of power now and very reliable.

I also just picked up a used flywheel we will be taking some weight off of and seeing how that helps or harms! I have some left over stuff if you need anything let me know and have fun!

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I just recently acquired a 86 xr80r as well. Thing smokes like a banshee. Wondering how your build is holding up. Any bolt on kits available that you know of? Thanks, any info is appreciated

 

 

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