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79 XR500 "Build"

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Hi all,

This is my first post on here so hopefully I don't mess it up. Also hope I don't piss of any "purest" people out there as this is in no way a restoration and I have no interest in restoring it to original. 

This is what I have been working on the last few weeks. I picked up an xr500 about a month ago for $300, it started but had no clutch lever so I didn't get a chance to ride it. I noticed later that it has a White Brothers aluminum swing arm and possibly upgraded shocks but I really don't know.

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Its pretty rough but a running bike for $300 I wasn't going to complain.

I decided i wanted to build it into something that was kind of a cross between a bobber and a scrambler and use it mainly for commuting across town to work, but still be able to tackle mild single track.

I went though my garage and was able to come up with a front fender off of a newer honda 150r (i liked how small it was), and a rear fender off of an 04 crf250x so it has the licence plate holder an led brake lights. the front fender bolted directly on but he back took some modifying.

From ebay I found a 21" wheel for the front (81-83 xr500) but the drum was a 131mm max dia while the original 23" was a 141mm max dia. this was quite a disappointment but I guess i should have done a little more research. I ended up putting the brake hub from a 83xl250r into it, its not perfect but it works for now.20171011_153611.jpg.1dda77cc0b2bcfb991791054bb946046.jpg

I then started to build a seat, while the original was quite comfy, it did not have the look I was after. I started with cardboard until I had a shape I liked. Then I cut, bent and welded it all together, luckily at work I have access to a nice break, shear, welders and scrap metal.

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It turned out ok I thought for my first attempt at a seat pan. Next I put some closed cell foam on it from a sleeping pad I got from the sporting goods store. I wanted a low profile for the look so the thickest part is only about an inch thick. I used a steak knife to trim the foam and it worked alright, I ended up covering all the edges with gorilla tape to smooth it out.

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I then covered it with marine vinyl I found at Jo Ann fabric. Instead of cutting and sewing to get the material to fit right I used a heat gun which stretched the material enough for a "good" fit. I used 3m spray glue and a metal plate on the bottom to secure the cover, its holding so far.

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Here it is with the seat all finished. I also found some horrendously cheap foot pegs for a yz bike from (99-05), I think they are a cast steel of some sort. I guess you cant complain much for $15. they required a little grinding to fit but seem to work good enough.

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I was finally able to take it out this last weekend and had a blast, it runs way better than a $300 bike should. I had to remember how to engine break as I usually ride a 2t with good brakes, it turns out they went away from drums for a reason. My seat wasn't quite as bad as I thought it would be out on the single and double track. We also went out to some hill climbs and the 500 impressed me with amount of torque it delivered at any rpm. This bike is much different than anything I've ridden before between its torque and having almost no weight over the back tire.

As far as the seating position goes, I actually like how compact it feels. I also think the low profile seat goes with lines of the bike rather well so I'm pretty happy with how it turned out, especially for being my first try at making one.

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Next for this build I would like to make it street legal. I'm not looking forward to figuring out whats going on with the wiring and converting from 6v to 12 as the components I have are 12v and i would like to have the front light be a LED light bar. I have a different bike that I am thinking about adding lighting to using a rechargeable battery like a Milwaukee m12 or something, so maybe I will go that route.

I would also like to figure out an exhaust for this at some point so i don't get kicked out of my neighborhood.

Thanks for reading, I'd love to hear what you think and any suggestions you may have.

Edited by megadillberry
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Gearbox's my have been ok in '79, but by now it'll be fairly worn, so take your time (and clutch) when changing gear.

Cant stomp it through or powershift or it will grenade. Any problem  jumping out of 1st?

pain bearing head and  no oil filter , (only a screen inside left-hand engine cover),, so change oil often with good mineral or semi-syn but not full syn.

no muffler can burn exhaust valves,

   GET AN AIR FILTER!

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Gear box feels solid so far, it never jumped out of gear or anything. When I took it out I definitely was pretty easy on shifting. The clutch/ trans set up is basically the same as an xr250 right?

I changed the oil once so far and plan on doing it before taking it out again. Not sure how much time was on the previous oil but there was no aluminum or anything so I'm hoping the head is still pretty solid. Good call on the synthetic tho, I didn't even think about that. 

Its got a pod air filter on it, I know its not great for off road but we rarely ride super dry trails (at least I wont be on that thing). It actually helped the motor out a little as it was running pretty rich, its still rich but not as much. If it was a trail only machine I would absolutely stick with the stock set up or something similar.

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Oil volume isn't great either,, treat the 'full' mark as the minimum and run 200ml more as standard.

Oil level is checked with dipstick sitting on threads,, not screwed in.

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I bought  a  new xr 600 in 1996.A neighbor  had a 1979 xl 500 with a rotten exhaust  that could  smoke my 600in a dragrace   every time . It did great wheelies  too.

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Nice unit! Those old things in running shape are getting harder and harder to find!

Hopefully somebody can correct me if I am wrong, but I believe those motors are susceptible to the cam journal/bearing wear due to lack of lubrication. I got burned with my 77 XL250 where the cam bearing journal wore so badly my only option was to replace the bearing with a needle bearing and line bore the head for a oil feed to the bearing. That occurred after I spent some coin and time restoring the bike - only for it to stop running 10-15 hours after I got it running. Really, my own fault as I should have done some research first but I just dove in and got it all nice instead. I understand if the motors are taken care of, regular oil changes, no crazy abuse, etc it isn't always a problem, but I think mine didn't see an oil change for over a decade before I got it. Unfortunately, the cost of the repair on mine put me way over on budget for the bike, and I shelved it.  

Long story short, you might want to check and see how your valve train looks like - maybe prevent some grief down the road. Again, I'm not sure if the 500s have the same issues, but if they do, might be worth checking out. 

Good luck with the bike! I always like to see people working on keeping these old suckers alive! 

 

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Thanks for all the feed back! This has been a fun little project and I'm glad you guys are liking it.

From all that I have read and heard, the journals for the cam is the weak point on the motor. I'm sure having no oil filter besides a screen cant help the situation either.

I think I will leave everything in the motor be for now. It runs very strong and starts first kick as long as I get it on the compression stroke, also it has not issues with stalling randomly and it idles very nicely. Wouldn't checking the valve train entail dropping the motor from the frame? Maybe if I can find some time this winter I will dig into it.

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I don't know if you need to drop the motor. I have a service manual for mine, if I remember I'll check. Pretty sure it covers the 500 motor as well. Even if you do its not a crazy hard task. 

I remember when I was talking to XLint Performance they said it doesn't happen to every motor, depending greatly on how it was maintained. If it runs good and oil changes are done regularly it will probably be good but always something to keep in mind. 

 

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It was definitely in the back of my mind when I took it out, I have no idea how much maintenance the previous owners did. I don't think it has had the easiest life based one the rear tire and some other clues. If you look at the first two pictures it looks like it may have been involved in some sort of burnout contest because there is no tread in the center. On the other hand it must have had some type of consistent maintenance based on how well it runs, they had also drained the gas before storing it. 

Oil is cheap so there's no excuse for not changing it often.

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valves cab be checked in place,, bit fiddly but ok. .05mm inlet and .08mm exhaust. piston at or slightly after TDC on compression stroke.

Magnetic sump bung good idea too. Lean bike to the right, and pull bung every couple hours riding to look for metal.......

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Awesome Muzz67, thanks for the specs! Seems like they can be hard to track down even on newer bikes if you don't have the service manual. Magnetic bolt is also on my list for this bike.

I know theres a whole mess of info on here about converting to 12v. I'm thinking I will try getting a 12v regulator and see what happens. Has anyone done this recently, I cant seem to find the Moose or Trail Tech regulator that I have read about. I have seen the $50ish Trail Tech regulator that requires floating the ground. If there is one I could just wire up that would be my preferred option. I want to run LED lights for everything (front rear and brake).

Every time I think I know what I need I end up confusing myself further. Right now my current questions are:

*does the stock set up output AC or DC voltage?

*did these come with a rectifier?

*does single or 3 phase matter?

*what all will I want from a regulator if I get a universal one off ebay?

*why is this so confusing?

 

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I'll have to see if I can find my service manual. I meant to look last night but forgot. It would help answer your wiring questions.

I'll look tonight (will try better to remember!). 

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