Rebuilding engine looking for suggestions for engine Mods

xscaferacer · Full Member Joined: Jan 29, 2007 Posts: 35

Does anyone have some good combs for engine mods, for street use? I have to re bore and go 20 over already. I was thinking of having it flowed, fly wheel balanced, bigger values, and port matching. Any good hits, I'm not looking to race or spend any high dollars, just looking to give it a little more! I know stock it rock and the more you do the bigger headaches.

Kablazzie

A new sump strainer.

Port work is a plus.

xs1961

yep, have a port job done,add 34mm roundslides & aftermarket headers/ free-flow mufflers. Boyer ignition.18 tooth engine sprocket.
I reckon the valves are already big enough, It'll never rev any higher without the motor(and you!) suffering !

grizld1

Yep, stock valves are plenty big unless you're doing major performance building.

If you already have to do a bore job and want a bit more giddyup without sacrificing reliability much, consider a pair of Shell-JE 77.5 mm. pistons; they bore into the stock sleeves for around 700 cc's and are domed to deliver a moderate compression ratio. At $270 a pair complete with rings and light tapered wristpins, they're probably the biggest bang for the buck if you need pistons and a bore job anyway.

I've been using Venolia 77.5's (about 1/2 oz. each heavier than the Shells) for the last couple of years; done right, a 700 conversion is a smooth as a stocker. Add a good port job and the results will have ya smiling.

Jack · Full Member Joined: Mar 15, 2005 Posts: 411

For street use where low to mid range performance is important,stay away from over-size valves as their benifit of increased flow won't be felt till higher up in the rpm range,just not practical for street use beside there are other tricks one could use to increase the percentage flow to enhance low speed performance. A good port job,depending on the available matearial you have to work with in the ports should yield a flow increasement of 15 % and 23% on the exhaust. For camshaft selection use either the Shell # 1 or one of the new Megacycle profiles that is comparative to the shell #1 in the lobe seperation at .040.

Griz has a very strong running XS that Ive riden,so just follow his advice and you won't be left cratching your head wondering why your engine combination performance isn't what it should be..................Jack

xsjohn

Ok.....since you asked............I am doing things that hopefully lead to longer engine life.........and add perfrmance for stock engines.....don't raise compression....make the best of stock......

Dimpled the piston skirts for better oil retention for skirt lubrication....discussed this with Falicon and they agreed this could help retain clearances after many thousands of miles......currently 50,000 on original pistons......lightly sand the edges of the new rings to remove the bur and prevent the slight gouging effect new rings can do to the cylinders.....after doing this mine still has 150 psi on both cylinders after changing the rings 10 thou ago.....been doing this for 35 years on every set of rings I have ever used or installed.........

Add top end cooler to reduce peaks in the temps during the summer that can overheat everything causing damage......also reduces lower end oil temps to 170 degrees n the summer........sure can't hurt.......

Bore the main bearing holes 15-20 percent to assure oiling because of added paper oil filter.......which reduces oil flow 15-20 percent.......

Run the fuel mixtures as rich as possible.....checking plugs for for ever so slight fuel smuge on you finger from the edge for the plug on both cylinders.....too much smuge is working against engine longivity.....no smuge is too lean.....

Retard timing 1/8 inch so the rods and crank don't take a beating from lower rpm's.........won't notice loss in performance and lower grunt is enhanced.....

Recently but not totally tested .....oiling the intake valve tips......

Gear the dang thing higher so it doesn't rev it self to death on the highway.........

Jack or Griz to do your head..........

Smooth the outside of the cam chain with some 220 and a block of wood...lay it out and go over it intil it is slick like glass....then slightly smoothe the sanded edges so they are not sharp......should double the life of chain guides....make sure the washer on the guide is the newer dampened one.....80 on up one I think.....reduces snatch on the chain......center the chain wheel to the front guide percisely....so it doesn't ride on the edge for the guide causing premature failure of the guide.....

Put gasket sealer on both sides of the lower cylinder gasket so it won't leak cause if it does you may have to go back.......been there and done that....

Don't let your friends ride you bike if the are beginners or want to bang your unwelded crank.........there is more but can't think at the moment...

John

grizld1

Sorry, John, I don't do port work. Jack's the go-to guy for that; he's doing the head for my next build.

BTW, I think you're really onto something with the supplemental oiling to the intake tappets; and those modified tappet covers look trick as hell!

xsjohn

Thanks .....will find out soon if I am wasting my time with this oiling thing .... will post a honest evaluation when I check it out....hoping for .004 or .005 on the intakes quietly...."if wishes were horses beggars would ride".......know what I mean......when are you getting your lastest running...bet it will fly....I am so scrany that if mine ran any better I would crash.....being so old as I am......I removed 75 lbs from mine by being a 135 lb weakling........like ttmaniac said...it's like a bike going down the road with nobody on it.......where is that devil anyway......

John

xscaferacer · Full Member Joined: Jan 29, 2007 Posts: 35

Killer thanks for the info. Ok nix the values. Should I have my crank welded? ANd with the 700cc kit how much other stuff does that affected?

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

Another thing you might consider are the elephant's foot valve adjusting screws. They must be installed with the rockers out so now's the time to do it. You will probably find some of your original adjusting screws dimpled and pitted anyway and in need of replacement.

grizld1

Re. the crank, that really depends on how tight you wind 'er up and history of the crank assembly. If you keep the rpm's to 7500 and below and the crank has never been apart, you're pretty safe from flywheel separation. If you hit redline or a touch beyond on a pretty regular basis and/or the crank's been pressed apart, it's a good idea to have the pins welded.

Re. the 700 pistons, I'm not sure if this is what you're asking, but they work just fine as a stand-alone mod and do not force other changes.

xscaferacer · Full Member Joined: Jan 29, 2007 Posts: 35

THANKS, grizld1. what do you think about having the fly wheel balanced?

grizld1

It's a nice thing to do if you can find a shop that'll do it well. I had Crank Works do a balance job recently on a crank I was having rebuilt. They wound up adding 8 oz. of weight instead of taking down the high side (and no, I hadn't asked for a flat track heavy-crank treatment). Needless to say I wasn't real excited about that, or about having to send the crank back because they'd forgotten to weld the pins, or about the 12 week wait for the job.

xsjohn

Falicon didn't weld my balance job......I never ran it over 5500 ever and it finally crapped a center main bearing and when I put it on the dial indicator it was 16 thou out........when the bearing went it must have shifted the wheels....maybe visa versa...?......who knows.........I think I can attribute the whole mess to lean 80 carbs pounding the thing to death.....those were bad days.....I pussied the thing and it still hosed.........450 dollars gone.......and untold hours of hassel.......

John

xscaferacer · Full Member Joined: Jan 29, 2007 Posts: 35

So, John, in the end I should waste the money or the time?

xsjohn

If the crank you have doesn't vibrate to where it drives you crazy I wouldn't touch it.....my first crank vibrated so bad that I had to have it done.....the balance was an improvement but it never ran as smooth as the stock 78 I have in it now even after the balance.......have no idea why.......just a bad experience.....and the lean carbs........retarded timing about 1/8 inch also seems to settle it down without any noticable performance loss......when I put it back on the F....I always end up retarding it back to 1/8".......

John

xscaferacer · Full Member Joined: Jan 29, 2007 Posts: 35

I have a 1981h, I did think I could retard the timing?

xsjohn

Have to grind the two factory screws off the pickup coil so you can swing it forward 1/8" and replace with some screws that are just like most of the screws on the stator..the slot in the pickup is long enoug to do this.....mark it where it is now for future reference.....there will be enough sticking out so you can grab the ends and turn them out with some vise grips..and replace with screws....it is already threaded into the stator.....

It will make it run along smoother at steady cruising throttle....2500-3000 or so rpm...and act like an engine should.....and then if you add my needles and it will go like hell when you crack it....and keep the cylinders 20 degrees cooler too........been dicking with this exact thing for 10 years....forget all the expensive mods and do this first......if mine ran any better I would crap my pants........

Raise the gearing.....18/30 is great if you don't weight too much or ride double a lot....mikesxs has all that....18 32 ect if not........I am 18/29 and love it.....onto the express an gone....stock 17/34 sucks......

John

royfisk

Here we go again guys, wheres tt when you need him. Everyone has opinions. Motor building is not rocket science. First step in building a engine is to make a checklist.
#1) Determan what exactly you want the motor to do.
#2) What gearing are you useing?
#3) determan what rpm range you plan to run in
Now you have a point to determan what components to purchase and use.
Pick a good quality cam that yes is designed to work in your rpm range
Pick the carburators that work best in that power band
#1 thing to not skimp on in any part of performance engine building is head work. All the high dollar add ons will not work if the ol girl loses her breath. This is true at any dissplacement includeing stock. probably the absolute biggest bang for your buck going. Theres alot more performance in a stock engine hidden there cause it is choked up on the exhaust side.
Rule of thumb for engine building
smaller mm carburators and longer intake passages build more low end tork and great stree rideability.
For wide open throttle drag raceing bigger valves, carbs and wilder cams.
Theres about 7 different real cam grinds out there. Pick one from a good solid manufacturer. Ive seen cams from hong kong fooie with exact matching grinds supposeofly as reputable cam grinders, but they dont work the same, nor do they wear the same.
As for the fancy electronic ignitions if you can tune points ignitions and time them why bother spending the extra cash? Poits work well up to 9000 rpm and then they will float. But if its street riden how much 9000 rpm will it see? I know that will start sh_t. Ive heard it before I dont want to be messing with my points all the time. Truth is if you do it right you wont be messing with them all the time. I bought a bike last fall and when I asked the original owner when the last time he changed the points he said it was electronic and had never had a problam with it. THE BIKE WAS A 77 WITH 12,000 MILES ON IT. When I got it home I checked the points and cleaned them up a little. tuned it and there still in ther today. So ignitions are cool if that 2-400 dollars are burning a whole in your pocket, or you simply do not want to take a few minutes to maintain your ignition system. But in my book that is headwork money. If you have stock electronic why replace it if it works. This is the most accurate timing of all ignitions. It triggers from the crankshaft not the cam. Therefore cam chain slap does not effect timing and it too is good for 9000 rpm.
If your on a street buld budget of bellow 1000.00 for engine work its a no brainer
heads 400.00
cams 150.00
carb kit 250.00
gasket and seals 150.00
2 cases of budweiser 40.00
send spouse to movies so not to disturb you 10.00
thers the best 1000 you will spend on your stock 650
now big bore add piston and boreing charges probably another 500 for the 700

xsjohn

Dang Roy ........whats wrong with just fine tuning the stock engine.....it's only a 650 and if any logivity is wanted just fine tune whats there.......the stock electronic ignition is fine with some tweaks.....that stock 34 carbs are great with some tweaks....the stock cam after adjusting the above pulls right off 2000 and goes way above what I would chance...........by the time you make it run like a 1100 and it blows you have nothing....one could have bought a 1100 and have both....and maybe a car and a vacation......and some beer...and some sanity......which I have lost and foud again dicking with this thing........find the joys in what it is....there are some....

John

royfisk

John you are right There is alot there, But some people like more and I do myself. did you actually listen to what I wrote? My personal bike will be stock bore built for low end tork street. Again and Ill argue this all day long bud is porting. If I were allowed only one mod on my engine it would be porting. John is your ride ported? If not why not? Your capable of doing it and its not going to cause you breakdowns or do anything except show you what you have been missing. while your at it why not add about 1 1/4" to your intake manifolds. now try that out boss and see how you like me now.

xsjohn

No I havn't done any porting......should and I am sorry if I didn't read between the lines on you post.......you know me I am intellectually challenged.......

John

grizld1

Amen, Roy; gotta know what ya want before ya do it, and there's nothing wrong with breaker points as long as you keep an eye on the ATU. If the mill's gonna see much of rpm's north of 7500, performance rods on a welded crank are a real good idea.

"Find the joys in what it is." Well yes indeedy, John, I entirely agree! But the old XS650 is different things to different folks; to me, from the time the first XS1's hit the street, it was a price point machine not worth riding as delivered, but a fine platform on which to build a motorcycle, and I find much joy in that.

xsjohn

Yea....think I reved mine to 4200 rpm today.....that was to pass a truck on the express so I could get home cause I was freezing my ass........

John

What Happened to 650rider.com?

Yamaha xs650