New to me 02 XR70

[apbling]

I just snagged myself an 02 XR70 and a 06 cfr50 for just a hair over 1k. Both bikes are super clean and only show a little wear on the case covers from shoes rubbing.

 

The cfr50 runs like a top. The XR70 runs ok, but I think it may need a little carb TLC. Guy said he had to clean it - he seems somewhat knowledgeable, but I'll end up taking a peek in there anyway because the bowl o-ring is starting to leak a little. I can tell it's not perfectly clean or setup because it seems a little doggy and coughs a little when you snap the throttle open.

 

Anyway, neither bike will be ridden much for a while - the 50 is for my younger boy who isn't ready yet, the 70 for my older boy who's still on a 50. I was thinking about riding the 70 myself a little.

 

Anyway, I was looking at what can be done for mods on the 70 - and from what I can gather, air filter and exhaust will help some, but the best bet is the tbolt 88 kit w head and carb, right? I'm really not interested in dropping big cash on an exhaust either.

 

Is there any other less expensive or intrusive mods I could do now for me to ride, remove easily when kid wants to ride it, then put back on as he progresses? I already plan on the 13T sprocket up front - I kept running out of real estate trying to get it into 3rd when test riding it - sure seems geared tall.

 

All in all, for 1k I could not pass up this deal.

[dirtbkr188]

Personally, I think the kit linked below is the best bang for your buck, you use the stock head and exhaust and still have a peppy little engine with the bigger carb and the street cam.

TBW0931

[apbling]

True, likely good bang for buck, esp if the bike already needs a top end freshen up. I haven't done a compression test on it, but it doesn't really show signs of needing a top end job. I know the carb isn't doing it's job 100%, so I hope that helps some. I guess I was a little disappointed with it - thought it'd be way more snappy than the kids 50...it is quicker and more powerful, but not by leaps and bounds. Then again, maybe that 13T sprocket will help.

[apbling]

One thing I remembered today as I was poking around this site...

Both of the CRF50's I own - about 75% of the time when I wind it out a bit in 1st, shift into 2nd and get back on the throttle hard, it'll pull the front end up a little. (now, maybe my big ass hanging off the back is the reason..) but the XR70 won't do it.  Maybe its a function of where I'm sitting on the bike (further back on the 50 due to smaller bike) or the 70's tall gearing, but it sort of adds to my thinking the 70 isn't running top notch.

Edit - did some more research - I didn't realize not only are the sprockets different between the 50 and 70, but it does appear 2nd gear is quite a jump from 1st in the 70...

Edited September 5, 2017 by apbling

[dirtbkr188]

1 hour ago, apbling said:

 it does appear 2nd gear is quite a jump from 1st in the 70...

That is partially due to the final drive gearing, but also because of the difference in the primary drive gearing. The 50 has 17/69 and the 70 is 18/67.

Both engines have the same identical trans sets.

[ohiodrz400sm]

You don't need the head. The 70 already has bigger ports than the 50. I would recommend just buying the $124, 88cc kit and source an actual Keihin or Mikuni 18mm carburetor.

 

Imo 1 of the best performance upgrades is a manual clutch conversion. With the above mentioned mods, the bike has a healthy punch off idle and in low to mid range. The auto clutch robs all of that snap. It's about the most forgiving manual clutch you'll ever come across and perfect for teaching the young ones. The only real downside is it must be in neutral to start.

 

If don't do the manual kit atleast put a heavy duty auto clutch in if you plan on hopping on and having fun with it.

 

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[apbling]

Ohiodrz - I think the current plan would be to leave the engine and clutch stock.  I think that hoppin it up would be a great idea once the youngster is ready for it.  He's a smaller kid currently, so if the time comes where he's ready for more power or to learn how to use a manual clutch, I'd likely be inclined to do that to this bike.  That way he can learn the manual clutch on a bike he's already somewhat familiar with, instead of giving him a 125 or whatever and also having him learn to use a clutch.

So, for the time being, I think I'll do the front sprocket mod, new chain (it's likely due for chain and sprockets anyway...) and maybe just fiddle around with a pod filter for something to keep me busy. haha.

As for the HD auto clutch if I ride it comment - are you saying if I get an 88 kit and I ride it I should do the clutch, or are you saying if I ride it AT ALL (all things stock) I should get the clutch?  My riding would be slow and casual, little hills (WI is pretty flat...) and mainly be in farmer fields.  If I need more oomph, I'd drag my ancient 1975 125 relic out of the garage...

[ohiodrz400sm]

If you hop it up get the clutch. The extra power is hard on the stock springs and plates.

 

The pod filter is actually a pia to take care of, especially off-road. If you're riding in any mud or puddles I'd leave the stock filter box on for now.

 

The 13 tooth will definitely help. It will make 2nd more usable but 1st will be really low then.

 

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[apbling]

Well, currently the plan would be more trails and fields and avoiding mud.  Sure, I could take the bike through mud and puddles, but my son's 50 would have a hard time, plus with the training wheels still on it limits his riding areas.  Kid needs to grow so we can ditch the wheels!

As far as being a PITA, do you have first hand experience with a pod on a 70?  Is the gain even noticeable?

I had a kawasaki 550LTD a few years ago that was an absolute pain to the get the carbs out with the stock airbox.  I put pods on, spent days getting the jetting just right and experienced 0 gains - sure it made taking the carbs out easier, looked nicer and gave you the feeling of more power with the sound of the air sucking in - but I ended up going back to the stock airbox because on windy days or on the hwy, the outside carbs would get more/cooler air, and the inside two wouldn't (or if a strong wind from one side was present, the left hand carb got more air) and it would surge and sputter... wasn't worth it.

[ohiodrz400sm]

As far as being a PITA, do you have first hand experience with a pod on a 70?  Is the gain even noticeable?

 

 

Not on a stock bike. The 1st mods to my daughter's CRF70 were an FMF exhaust and BBR carburetor kit with pod filter. The larger carb with pod filter does make a big difference. I suspect a pod filter on a stock carb does little to nothing.

 

On a side note, she ended up roasting the intake valve riding back at our track on a muddy, rainy day when I wasn't around. That's how I ended up with the TBPARTS Race Head.

 

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[apbling]

Yeah, I'm second guessing the pod filter now.  Likely won't do it if there's no actual performance benefit.

As for roasting the intake valve - was this because water was taken in through the intake?  I only heard (and experienced once) such a thing, but thats when it was real lean

[ohiodrz400sm]

The filter was saturated. It ate enough muddied water that it either pitted the seat or cupped the valve. I've never gotten around to actually looking to see what the exact damage is. I just know it doesn't seal.

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