XR100r project for fall/winter 2021

pidjones

Over 1,000 Posts
A good friend bought an old 2001 XR100r fr his grandkids to play on. Needed rebuilding so he disassembled it and bought gasket kits and scrounged up some missing/damaged parts. Then, his hands started giving him problems and he can't reassemble it. So, I've brought it all home and started.. But, right off the bat the cylinder is bad beyond honing (.05mm taper and serious rust damage). There are no machine shops around here that do motorcycle cylinder boring. I know that I can send it off and for ~$90 get it bored out from ~53mm to 53.25 or 53.5mm but add in the cost of pistons, rings, wrist pin and shipping and it is more than a big bore kit. So, I'll be ordering the TB kit soon. Gonna reassemble the transmission, clutch, crank and such first just to make sure there are no surprises there. I'll get some photos up before long.
 

Rat_ranger

Coast to Coast
They are dirt simple and the TB 120 kit adds a noticable bit of power.

I've got one swapped into a cr80 chassis, and I have another bottom end with a kitaco short stroke kit. Keeps it at 100cc, but big bore/short stroke, supposed to peak around 14hp at 13000rpm. I'll swap it into the xl75 if I keep it.
 

pidjones

Over 1,000 Posts
Well, Tuesday @ the Time Warp (great turn-iut this week) I enquired and of course these guys knew of a local shop to bore the jug. I called and the price seemed right so will take the jug and old piston in tomorrow. I'll let him tell me if he wants me to order .25 or .5 mm over piston and rings. Meanwhile, I sorted transmission parts (he had bought a spare due to some ham-fisted work by a PO). They are cleaned and laid out, but two 6201 bearings felt rough so their replacements are on order. The other bearings feel fine and the side clearance on the rod's big end is well within spec.
 

Maritime

Over 10,000 Posts
Nice, sign me up to follow. Ham fisted PO. Mine broke the valve tappet cover and set the valve .003" to loose LOL.
 

pidjones

Over 1,000 Posts
Jug is still out for bore. Meanwhile, with the new bearings received, the bottom can go together, right? Until discovery of a badly worn cam chain drive sprocket. Off to O'reilly to try their bearing puller and with the aid of a hose clamp around the arms to keep the puller on the gear it came off. Added to the Partzilla list that awaits the call from the machine shop to get rings and piston. Otherwise, case together temporary-like to keep parts in order and ckean. BTW, it was a lot of fun picking through two transmissions to select the best parts to assemble. My friend is one of the best mechanics I've worked with (we made a hell of a team teaching and trouble shooting broke cyclotrons), but his hands didn't let him organise things like he normally would.
 

Rider52

Over 1,000 Posts
Good luck with Partzilla. Their shipping has been awful. It took me 4 months to get the rubber bits for a 750 battery box and they were listed as in stock.
 
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Rat_ranger

Coast to Coast
The xr80 and xr100 transmissions have different ratios. A lot of people switch to xr80 trans for the taller 1st gear.

The XR 80 has 2.992, 1.823, 1.40, 1.130, 0.96 with primary at 4.437.

The XR100 has 3.083, 1.882, 1.400, 1.130, 0.923 with primary 4.437.

If you get the takegawa 5 disc clutch it changes the primary to 3.833, and overdrives the oil pump for increased flow.
 

pidjones

Over 1,000 Posts
The xr80 and xr100 transmissions have different ratios. A lot of people switch to xr80 trans for the taller 1st gear.

The XR 80 has 2.992, 1.823, 1.40, 1.130, 0.96 with primary at 4.437.

The XR100 has 3.083, 1.882, 1.400, 1.130, 0.923 with primary 4.437.

If you get the takegawa 5 disc clutch it changes the primary to 3.833, and overdrives the oil pump for increased flow.
Nice info to have, but he just wants it to start easy and run smooth for grandkids to ride.
 

pidjones

Over 1,000 Posts
Good luck with Partzilla. Their shipping has been awful. It took me 4 months to get the rubber bits for a 750 battery box and they were listed as in stock.
Hope it doesn't go that way, but I've had good service from them in the past. Of course, since these are Honda parts, there are plenty of alternative sources.
 

iatethepeach

Coast to Coast
I recently had the same problem with Partzilla, unfortunately. All the parts in my last order showed up as "in-stock" on the website. After I submitted it they sent me an email saying multiple items were delayed. I called and asked if they'd ship the stuff they had right away. They held up the whole order until all the parts became available.
 

pidjones

Over 1,000 Posts
I've contacted Partzilla to ask them to check my list and see if everything is available. Still waiting for the machinist to call with the piston size needed. There is no big hurry, but I want to get this out of the garage by Christmas.
 

Rat_ranger

Coast to Coast
Parts in general have been slow since covid started. It took a dealer I worked at 4 months to get a starter relay for an MT03. Partzilla is annoyingly slow at shipping when everything is supposedly "in stock."

The little XRs are great playbikes. With the low 1st it's easy for people to learn without stalling constantly. They can be hopped up pretty far depending on what you are willing to pay. But basically stock will run forever with an occasional oil change. One nice upgrade that stock or not can use is the takegawa clutch cover. It adds a real oil filter, and changes the clutch arm for a lighter clutch pull.
 

pidjones

Over 1,000 Posts
Partzilla had everything available except the cam chain drive sprocket. Had to order it from CSMNL. The machinist called and said .25 over did it fine, so piston, rings, new wrist pin, clips, cam chain, cam sprocket, and tensioner are on order. The rest of the bottm end is together.
 

pidjones

Over 1,000 Posts
Partzilla parts due in Monday. Matthew really went the extra mile and did me good on chasing availability.
 
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pidjones

Over 1,000 Posts
Partzilla order came this afternoon. I'll take the piston and rings to the machinist tomorrow to let him check the size. Cam chain drive sprocket should ship tomorrow from Netherlands.
 

pidjones

Over 1,000 Posts
I have the cylinder and parts now - everything (I think) except the cam chain drive sprocket, which had to be ordered from CMSNL. They first claimed ship would be 14th (yesterday), now saying 16th.
 
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pidjones

Over 1,000 Posts
DHL has the cam chain sprocket leaving the Netherlands today! Due here by Tuesday. Need to prepare the GL1000 or Rd400c or both for vintage show at Honda Knoxville this Saturday. This morning measured ring gap, adjusted the top ring gap just a touch, and put the rings on the .25 over piston. As soon as that sprocket is on I will be able to start real assembly of this little lump. I'd like to get it ready for him to have grandkids flailing it for Thanksgiving.
 

pidjones

Over 1,000 Posts
Sprocket came in yesterday but I had commitments to do some lawn maintenance for a widow. Put the crank in the freezer over night and after getting it out and putting in my WorkMate, heated the sprocket with my plumber's torch and dropped it on - dead on aligned tooth to keyway. It will all probably wait now for after Barber as we have our church bike show next Saturday (and I'm the organizer) plus Hnda Knoxville has a vintage show tomorrow that I plan to show both Geneva and the Hunley in.
 

iatethepeach

Coast to Coast
That's an impressive turnaround time from CMS! Sounds like the grandkids will have a Thanksgiving they won't forget.

David Silver is another good source for stuff like that sprocket. I use them a lot since they're nearby and don't charge a shipping fee if you pick up parts at their warehouse.
 

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