High Lift Cam Mystery

[RS Thornton]

I acquired a project bike awhile back and just getting to it. The motor has a big bore kit(wiseco 74mm), and was only partially assembled. It appears I have some sort of high lift cam, the cam lobe height is about 70 thou over stock, and it looks like it as 4H on one cam and 4N . Quesitons 1&2; Anyone know what this cam is or where it came from?

The head has been machined on exhaust cam follower area to get clearance, some of the intake was done but was not finished. I am pretty sure I handle the bit that is left and get clearance. What I do not know is if the valves and piston have enough clearance. I expect I can rotate by hand to see if it works cold, but what about hot and running at 7000 rpm? Q3: How to you know if you have enough clearance between valve and piston?

Any additional thoughts or inputs would be appreciated. I tend to run the motors stock so into new territory here.
Thanks,
Scott

[TADracer]

Cant answer your cam question but there were a few cam grinders that made aftermarket shafts for the XS11. But concerning piston/valve clearance, that is always a matter of opinion but I like to stay over .040" on the intake and .065" on the exhaust. I run stock cams but with slotted sprockets so that means I check piston/valve clearance once a year. But checking is a bit of a job if you have not set up to do it before.

First you need a pair of light weight springs that you can depress easily then assemble #1 cylinder with these and install everything including torqueing down the head and the camshafts. Then you should have a TDC tool, degree wheel, pointer and a 1" travel dial indicator. See pictures below.

Find TDC and install/zero your degree wheel and pointer. You can probably get away without the degree wheel and use the timing plate but you must check the clearances on both intake and exhaust every 5 degrees from 20 degrees before to 20 degrees after TDC because the closest event might not occur at TDC. So to be really accurate a degree wheel is a good thing to have.

[trbig]

You didn't state whether it was the early or later head/valves, but if the pistons are from Wiseco, they are a bit more domed than earlier 78/79 pistons, but less domed than the later 80+ pistons. So if a later head, you'll have a bit more room to play with, but if an early head, you'll have less.

There's Tadracer's MUCH better option, but most of us use the clay "Squish" method. You have to put a strip of clay across the top of the piston where it will catch both intake/exhaust valves. Re-install the head with a used head gasket, (Already been compressed) get everything in time, roll the engine around twice, then remove the head again and check the thickness of the clay. I've heard that .050" or thicker is the magic number, but his numbers make more sense since the exhaust is going to heat up/expand but intake won't.

[MPittma100]

Clearance

You might consider getting another correct cylinder head assembly with/cams and start over. Put the current setup on eBay or elsewhere. Checking piston to valve clearance with clay or dial indicators and degree wheels is your choice. Both work.

Decide what you want to do with the bike -ride or race? A big bore kit is installed to overcome a "foul" bore and not so much as a performance adder.

[WMarshy]

I'd be interested to know what the base circle and lobe dimensions are if you can. I might be interested in the cams...

How hacked up is the head, is it quality work? Got pictures?

[BowlingSS]

I have used the clay method on my old LS1 and it works great.
Good luck.

Bill

[RS Thornton]

Thanks for the input so far.
The bike is a 78E, and the pistons are Wiseco 4070PS(XC) which I think are obsolete now. I am thinking cam possibly from webcam racing and in looking at their web page I think I need to be considering a set of their valve springs.
Lift 435/.435 duration: 288°/288° duration at .05 260°/260°
Excellent upper end performance for racing engines. Requires Performance Valve Spring Kit, Shim Under Followers, and High Compression Piston.

The work on the head is reasonable for hand work, but was not done on a mill. This was a craigslist purchase a few years back and I got this 78E with big bore, and a frame(inc swing arm, brake housings, side stand etc) that had been powder coated in battleship grey. The bottom end of the motor appears to be properly assembled. My plan was (is??) to bolt it all up and ride it, likely with aftermarket cosmetic changes in lights, exhaust and seat.

I do have another 78E stock head with cams, valves etc and was ready to put it on the cylinders but then I found theses cams. I am thinking I might finish off the head work and set it up as it will only cost me my time. I can use the putty technique to check clearance and if it is off I can just go back to using the stock set.

[WMarshy]

Good luck, doesnt sound like that cam will have any street manners. Might not be a very good choice for street.

[RS Thornton]

Wmarshy, what is your idea for those cams? Any chance you have a set more matched to a big bore street setup? If I install them and they have no low end might be we can work sinething out. I am not overly ambitious about trying tune carbs, cams and exhaust.

[yamtom]

duration 288 and 260 at .050 dont sound quite right

Hi Scott, That duration and the 050 numbers dont sound right. I am most experienced with reading car cam stuff, but I would be checking that out to be sure of what you have. I assume you are taking info off a website, and not actually checking the cams yourself. In the long run, I doubt if that would actually make much difference, just knowing the two durations is what I mean. I have to think that with someone your weight, and a near twelve hundred cc engine, that tourque isnt gonna be too much of a problem. I would be more concerned about tuning, and the higher idle, and the general racket a big cam makes then enough power. I trust that you wont be using this bike for any of your marathon iron rides.

[WMarshy]

Wmarshy, what is your idea for those cams? Any chance you have a set more matched to a big bore street setup? If I install them and they have no low end might be we can work sinething out. I am not overly ambitious about trying tune carbs, cams and exhaust.

If they truly are the specs you quoted from Web Camshaft's site Im not sure I want to mess with them, needing an under bucket shim and all. I want to make a hopped up XS but that cam you quoted would be for drag purposes only and have no street manners. I want to stay away from anything that needs under bucket shims because IDK where you can get buckets for the XS for under shim. They would likely be one off items that you would have to get an aftermarket cam manufacture to make for you ($$$). If you can get me the actual lobe lift I could probably make my decision on that but duration would be nice to know. However, in general the duration is increased as the lift increases so you can make some assumptions based on lift. Either case, aftermarket cams from Web Cams or Megacycle Cams are welded up and ground from stock cams so they should carry stock markings unless they ground the grind number in the end or on the shaft somewhere...

Any stock set of cams will work fine for your big bore. If you want to get the most out of the stock cams then dig up some posts by Dan Hodges. He recommended a combination of stock cams (earlier and later) and slotted cam sprockets to improve power. Otherwise if you just want the best stock cams available search out some from a 78 or 79 and just bolt them in.

These are the tree cams offered by Web.
Yamaha XS 1100 (78-81) DOHC 8v
.365/.365 286°/286° 245°/245° 118 N/A 80-121 N/A
High performance street cam for stock engines. Price Per Set (2).

.395/.395 284°/284° 256°/256° 110 N/A 80-131 N/A
Strong mid and upper end performance for street / strip. Requires High Compression Piston, and Performance Valve Spring
Kit. Price Per Set (2).

.435/.435 288°/288° 260°/260° 125 N/A 80-141 N/A
Excellent upper end performance for racing engines. Requires Performance Valve Spring Kit, Shim Under Followers, and
High Compression Piston. Price Per Set (2).
Valve Springs Only VS-Y11
Dual performance valve springs. OK up to 0.440” valve lift. Stock retainers OK.

[WMarshy]

These are the 5 cams offered by Megacycle.
Grind: 254-00
.354" 254° 110° OK with stock pistons and springs. Slight increase in mid-range power for street/road riding.

Grind: 254-70
.380" 261° 107.5°/108.5° Best all around road cam. Must use springs #109-Y or #80-0449. Should clear stock pistons, must check, .060" VTP clearance is needed. Great midrange and added top-end.

Grind: 254-20
.417" 268° 107° Drag race, certain road race - long course, high R.P.M. power. Must use racing springs and pistons.

Grind: 254-10
.410" 250° 105°/108° Shim under tappets, racing pistons and springs are needed. Drag, torque, mid-range throttle response.

Grind: 254-60
.438" 258° 108° Drag race, competition use. Shim under. Must use racing springs and pistons. Max. cylinder pressure.

[MPittma100]

Cams

+1 on stock using stock cams.

The normal aspirations for anyone considering performance upgrades is - if it is bigger, it is better. This pattern of thinking almost always DOES NOT work.

Most people do not want to think about all of the many other things that it takes to correctly change a camshaft - PTV clearance, compression ratio, cam timing, fuel and exhaust mods, etc.

So, the most important question to answer is what is the intended use of the engine/bike.

If you are going to race the bike, these are possibly the cams to use if you perform all of the other mods. Street driveability will be gone, and pump gas will not work. Racing gas at $12-$14 /gallon will.

If you want to ride the bike everyday, choose the stock cams and cylinder head. Don't mod anything else until it is together and can be ridden to see if it "needs" anything. JMHO

[RS Thornton]

good news bad news

Good news. Positive ID as webcam 125 grind which are racing cams.

Bad news, no good to me!! I have no interest in putting money into followers or having a drag bike. Will put one of my stock cam sets in and call it good. Thanks for help. Next up is the mystery carb, please see my other post.
Scott