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Engine Build thread!
- Thread starter OutgunnedOverbudget
- Start date
You'll want to replace the front cam chain guide and if the motor has near 20K miles (or more), I'd replace the chain too. As far as the other stuff you've listed goes, personally I think the gearing is too high, and I wouldn't use an 18T front because of the clearance issues. Yes, these bikes do benefit from a gearing change, but only a small one. I like 17-33 on an 18" rear wheel, 17-32 on a 16". Also, if you still have the stock carbs and charging system, I would stick with them, especially the charging system. In my opinion, a PMA is no better than the original charging system and has a host of it's own issues and problems that could arise.
on the port, will you be doing it yourself? don't go crazy on taking material out of ports. Especially don't take down the ridges that mate to the pipes. Target 1.5" headers
More info could help Mileage known ?
is it to 77 mm and is it not $ 80 a piece
Rebore costs
VM 34 expensive
If early model small end conrod can be a problem
Is it for getting it running or other -- Inspection before can save costs
Compression test
is it to 77 mm and is it not $ 80 a piece
Rebore costs
VM 34 expensive
If early model small end conrod can be a problem
Is it for getting it running or other -- Inspection before can save costs
Compression test
Cam chain and front guide are a given when rebuilding these motors. 17/32 gearing works very well on these bikes. I would consider 80mm pistons instead of 77mm. This kit is pretty reasonable. Or if you want to stay with your stock cylinder block you can get just the liners and pistons. VM34s are a good choice. Stay with the stock charging system. Get a rewound rotor from Jim and a solid state regulator with a new bridge rectifier and it will be trouble free for years. I would go with a Boyer ignition. Have used them on 5 bikes all have worked very well and been trouble free.
https://yamahaxs650.com/product/447-big-bore-kit-80mm-750cc/
https://yamahaxs650.com/product/447-big-bore-kit-80mm-750cc/
+1 for the point from GLJ. I got great performance out of the 700cc kit from Gary Hoos and the head rework by Roger (https://www.xs650.com/threads/700cc-kit-with-a-shell-1-cam-in-a-78xs650e.65405/) , but still wondering about 'what could have been' if I had gone for 750cc.. Don't forget to upgrade the brakes and suspension!
OutgunnedOverbudget
XS650 Member
Yes, chain tensioner, and chain are going to be replaced. Thanks for the info on the gearing, I’ll be sure to run it that way!
I have most of the stock system except for the pickup and stator housing, which is why I was leaning towards a PMA system. I could completely replace the charging system without hurting the wallet. I do have stock carbs I believe they are BS34
@GLJ I definitely considered 80mm pistons!
@Jan_P My local machine shop quoted me 280 to bore out both cylinder liners (they’re in great shape) and I can get 77mm pistons for 151.00 Canadian shipping included, 80.00 is the price in usd.
Motor is a 1980, turned freely and had decent compression when it was together but pistons were ugly!
I’ll have to take a better look at my options for the charging system, Jim’s rotors are definitely something I considered !
@zrx1100 very light porting for sure, there’s a great thread here somewhere that lays it all out! 1.5” pipes are the plan for sure.
I have a front fork from a 96’ Kawasaki zx6, then set up discs front and rear
one more thing. You will definitely need to upgrade the clutch. I skipped that step and my clutch started to slip right away with the added horsepower. In the end I added vesrah springs with EBC fiber plates and the clutch works very well. No need to go full Barnett as that will create its own problems and is not necessary.
OutgunnedOverbudget
XS650 Member
I just realized I’ve been looking at your build for a lot of info haha, did you order direct from vesrah?
ordered from 650Central, but you can get those from Amazon, etc. MMM at 650 Central explained to be issue with Barnett springs. He had both types. After you replace the clutch, just use wet clutch specific oils too. I've been using Lucas 20/50 motorcycle non-synthetic oil since the rebuild.
Putting it out here
Everyone does own choices But i have seen tuning on old machines cost a lot of money and not coming so many miles before the
Catastrophe is a fact.
Even though 650 is on the small side depending on driver size and for longer runs
I feel the power and the oommph is enough for most riders If properly tuned .
Again ..it sounds as low cost job can get this machine running and giving many years enjoyment.
And a lot of money in and getting a lot of problems.
Again everyone does what he likes and wants .. And how he will ride..
Back in the day trying to tune an old Brit bike or old Honda was rarely a success story,
Sometimes a very bad experience.
OK this crank and machine has a good reputation But still telling it.
Everyone does own choices But i have seen tuning on old machines cost a lot of money and not coming so many miles before the
Catastrophe is a fact.
Even though 650 is on the small side depending on driver size and for longer runs
I feel the power and the oommph is enough for most riders If properly tuned .
Again ..it sounds as low cost job can get this machine running and giving many years enjoyment.
And a lot of money in and getting a lot of problems.
Again everyone does what he likes and wants .. And how he will ride..
Back in the day trying to tune an old Brit bike or old Honda was rarely a success story,
Sometimes a very bad experience.
OK this crank and machine has a good reputation But still telling it.
I take a slightly different approach. If I want more power, I buy a different bike!
I agree within reason. Extra power can be had without hurting durability, but pushing the limits and expecting a very old design to compete with modern bikes is unreasonable..
OutgunnedOverbudget
XS650 Member
@Jan_P keeping my finger crossed that this bike cooperates all the way through, luckily there’s a heap of information available for these machines
A modern bike probably would have been the easier route especially for my first bike, but I fell in love with these bikes and honestly have no desire to own anything else right now. Whatever happens along the way I’m happy to deal with it and I’m confident based on what I’ve read that I shouldn’t be pushing this motor too hard as long as I’m treating her right!
Rational thinking is a slippery slope. Go down that road and one will wonder why we are on this forum at all
for what its worth, I have ~3500 miles on my build and countless dyno runs. It has been great fun! I see the associated cost as therapy
on the latter, @OutgunnedOverbudget , the total for my 700cc project, with clutch and exhaust was ~ $3K, but I went with purchasing the block/piston as a kit from Hoos ($730 with the Shell#1 cam+gaskets) and having the head reworked by Roger from R&D (another ~ $750 with KW springs ($550 without springs). Hoos kit was on spec, other than me adjusting the gap on a couple of rings out of abundance of caution.
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I'm using the same set up for my future build. I have all of the stuff ready to assemble including a Vape ignition. Gary Hoos and others here on this forum have had nothing but good things to say about this combo. My point was that if you are trying to build the worlds fastest 650, you would be better off starting with a different platform.Rational thinking is a slippery slope. Go down that road and one will wonder why we are doing on this forum at all
for what its worth, I have ~3500 miles on my build and countless dyno runs. It ahs been great fun! I see the associated cost as therapy
on the latter, @OutgunnedOverbudget , the total for my 700cc project, with clutch and exhaust was ~ $3K, but I went with purchasing the block/piston as a kit from Hoos ($730 with the Shell#1 cam+gaskets) and having the head reworked by Roger from R&D (another ~$550 with KW springs). Hoos kit was on spec, other than me adjusting the gap on a couple of rings out of abundance of caution.
I have about $6500 total in my XS. But I did a majority of the work myself. I only farmed out powder coat, lacing wheels, and boring the cylinders. If I had farmed out all the fabrication it would have easily been 2-3x the cost. While I enjoy the bike a lot, it is definitely happier at 55-65mph than 70-75. You build a bike like this for enjoyment, not cruising the highways. While it can cruise 75-80 it definitely vibrates more than I like. But that being said when the weather is nice I do commute with mine.
It's a great city bike. But expect more tinkering than any newer bikes.
It's a great city bike. But expect more tinkering than any newer bikes.
