I was installing a 555 top end today. There seems to be a clearance problem with the pistons and the valves. I have not checked the actual clearance but I believe it is 0.00" It has MegaCycle cams (384-20) with 0.417" lift. They recommend 0.060" clearance.
Several options:
1. put the stock cams in
2. cut the pistons more to allow for the high lift (if there is enough material)
3. install a thicker head gasket (are there any problems with this?)
There was a board member (in CA I believe) who mentioned that he could machine the pistons for more valve clearance. I can not remember who but please post up. I may try searching for a past post later.
Looks like it am going to put the 500 top end back on until I can get this resolved. Getting good at rebuilding the top end. Can have it swapped out in about 2 hours. But not tonight.
Edited to remove the 'amp;' from after the ampersand (&).
What thickness gaskets are you using now ?
if you go with thicker gasket you will lower compression ratio, best bet is to trim the valve reliefs alittle, if you go with stock cams i wouldnt think it would breath well enough to be useful to the added Cubes, if you have an old headgasket, there is a trick with modeling clay on the piston to get a impression from the valve as it gets near the piston. then you messure the from top of pistion valve relief to indent and should give you ballpark idea of clearance. Bob B. step up if im wrong plz.
Using stock thickness gaskets. I have a thicker copper gasket that I have not tried yet. Measures approximately 0.028" thick.
I believe the pistons are Wiseco. There is an imbossed W with a circle around it on the inside bottom of the pistons.
Yeah, I was concerned running the stock cams with the larger bore and not having enough flow.
I will try to measure the clearances tomorrow. Someone had mentioned using a piece of solder to measure the clearance since clay can get distorted when removed and being measured. May try both methods.
Almost forgot...I have another head that has been milled and ported. I want to run it, so looks like increasing the valve reliefs in the pistons is the way to go.
Take the modeling clay and put some on the piston so it covers the valve relief areas. Make sure the piston surface is clean so the clay sticks. Put some lube on the valve face so it doesn't pull the clay up. Then do a rotation of the crank by hand (slowly). After the head is off. Cut the clay across the middle of the valve relief. Then you can pull off some clay and measure the thickness of the clay on the piston.
The cams I run have .438" lift. Never had any clearence problems.
I'm running JE pistons with huge domes for high compression.
.060 clearence is probably a pretty safe # in case you miss a shift.
I would think .050 is fine (minimum). The valve springs will be floating before the valves hit the piston.
Any machine shop should be able to take a few thousands off the pistons if needed. Also the valve seats could be cut more to fit the valves a bit further into the head. The stems will need to be ground a bit to get them within specs depending on your shim thickness.
I run a shim under bucket setup. It uses Kawasaki 13mm shims. They come in .002 increments. After I do a vlave job, I sometimes have to grind the stems to get the exact clearence with the shim available.
I just did a race engine (Ford V8) and I hand cut the valve reliefs in the pistons to accomodate the larger chevy valve train. I used the clay method and a die grinder and a lot of beer.
For cars, the valve manufacturers sell a deal that goes in place of the valve but has a cutting edge on it. You install the valve cutter, put the head on, spin it a few times and you're good to go. You can rent the tool from the valve manufacturer.
I would contact your valve manufacturer and see if they have something like this.
I would NOT do the hand cutting again. I would wait the two weeks shipping to order the tool.
Shane
306 N2O Pinto
That reminded me of some friends that raced Porsches. They made their own cutter by brazing a piece of hardened tool steel on an old valve.
Same method you talk about. Just homemade :mrgreen:
Just checked the clearance with clay (plumbers putty actually). No problem with clearance. The minimum was about 4mm. With that much I am going to put on the milled head!
Now I am really confused. When running, it had the same buzzing sound as when the valves float. I did the cam to shim clearance twice, so I know that is correct.
What else would make the buzzing/vibrating sound? If the head gasket was bad, would it vibrate and make a similar buzzing sound?
The head gasket can't make any noises. It's compressed between the head and cylinder. There's no part of it that hangs out to vibrate.
Valve float only happens at very high RPMs. If your valve springs are too weak it could happen at a little lower RPM.
I tried a set of APE springs once (I use Kibblewhite normally). They were Kawasaki KZ1000 springs for race cams just like the Kibblewhites.
But I had alot of problems with them. The noise (like valves floating) happened at much lower RPMs. I tried less shimming to change the installed height trying to lower the spring tension. I ended up breaking the tip off a valve where the collets fit. I don't have a spring tension measuring tool, so I can't compare the springs to see what was going on.
A buzzing sound could just be something else on the bike making noise.
Maybe a good set of earplugs will make the bike run better :lol: :lol:
I am running heavier springs that are recommended for these cams. I had this same head & cams on the 75mm cylinder without any problems or weird noises. It sounded like it was coming from the engine. Never really rev'd it above 4k but the buzzing/ticking sound was at idle as well. Oh well, it is all apart again, swapping heads. The intake valves had some odd wear on the seats. The seat was worn concave in a small area, very easily seen. So I ended putting another set in but had to neck them down first. Took a lot longer than planned.
Maybe it will go away......will find out tomorrow.
QuoteI don't have a spring tension measuring tool, so I can't compare the springs to see what was going on.
Basic home made Valve spring tester. Wooden or steel frame about 6" taller then a stadard cheapy bottle jack but wide enough for a cheap bathroom scale, place scale centered in frame, place jack in middle of scale and re zero the scale. using a section of pipe alittle bit larger diameter then most springs i test, i attach it to the top of frame work , i Cut/grind a slit up the length of the pipe. now place the springs on the top of the jack and pump watching through the slit in the pipe for spring bind or compression limits(glueing an old messuring tape to pipe is helpful) then read the scale for height of spring compressed. this may not be the most accurate, but good way to compare springs of same type.
Finally!....I figured out what the real clearance issue is. Guess how I figured this out, the hard way. I put on the milled head with the .028 thick copper gasket and every thing turned fine...by hand. Once the plugs where in this is where the fun begins. I tried to start it and heard a tapping sound, guessing it was just one of valve-shim gaps that was a little big. It would pop and blow really black smoke out the exhaust. Now why would it be running that rich? So I decided to pull the plugs and make sure they were sparking, in case I damaged a wire when pulling the head. When I removed the right side plug, it had a shiney spot on it. Thought I just rubbed it when I removed it. When I removed the left side, the electrodes where bent almost together. The pistons were hitting the spark plugs! Luckily no damage. There are not bent much but enough to close the gap and not let it run. At least GS plugs are cheap!
Now for the questions.....
Can I install thicker spark plug washers to raise the plugs?
Are there different length plugs?
I hate to install a thicker head gasket and loose compression. The only other option I can come up with would be to put the stock head back on. Advise?
EDIT: I guess I could pull out the portable milling machine (aka Dremel) and create a relief in the pistons for the spark plugs. Just not sure how much meat is there without pulling the pistons out.
You can put an extra spark plug washer on the plugs. The pistons I have came with a spot milled for plug clearence.
It sounds like the right side is just barely touching if it only has a shiny spot on the plug. The left side didn't completely mash the plug end either. So it won't take much to get some clearence.
Do I leave the existing washer and have 2 washers? Or should I just have 1 thicker washer?
I would use 1 washer that fits in the cutouts in the top of the cylinder.
It would need to fit in the cutout and allow oil to pass around the stud.
I think it would be easier to use regular o-rings. You could get some that are thick enough to make up the extra space. The head gasket will contain the o-rings in their position. They won't be able to blow out under oil pressure.
And the heat shouldn't be an issue. I have o-rings on my gsxr500 motor that have worked without problems.
:o :o
Oops I thought you were talking about something else.
On the spark plugs I would use 2 washers. But they should be spark plug washers, not regular flat washers.
That and a little dremeling on the pistons will solve the problem.
I got copper flat washers to use on the plugs. Is there a problem with using a flat copper washer with the regular spark plug washer? I am hoping that this will create enough clearance so I do not have to pull the head again and cut the piston.
Copper should work.
The washers fixed the piston-plug clearance issue by a little less than 1mm. There still is a tapping sound but sounds more like the valve-shim clearance.
It did not want to run. It will idle (sort of) but give it gas and it dies. The plugs are very black, so it is too rich. Before installing the 555, I dropped down a size in the main from a 147.5 to a 145 and lowered the needle by removing 1 of the 2 washers.
I am a little confused as to the required jetting. Would a larger displacement with a greater compression motor need to be run leaner?
I would think you need bigger jets. It may be too rich at idle. But when you
try to open the throttle there is not enough fuel for the air going in.
I have a air/fuel ratio meter. I installed an oxygen sensor in the exhaust.
The meter has different colored leds that show when it is rich or lean.
The problem I have is the race fuel destroys the sensor fairly quickly.
With unleaded fuel it wouldn't matter how long you played with the jetting.
But it is a great tool for tuning.
The tapping could be insufficent squish band clearance. When you had the motor apart did you notice any shiny wear marks on the perifery of the piston or head?
This month's RRW magazine has a very good article on race engine building. When I read it I thought of your ordeal Darrell.
:(
ARGH...SQUISH!!!!....do not talk about squish!!!! :x I have read too much about squish during my endeavor with 2-strokes.
I did not notice any shiney wear marks but then was not looking either. I did look for impact areas which I guess would look the same. Since these are used pistons, there may be some play with the pistons and the cylinder walls. I will pick up the RRW mag to see if it will help me figure out what I am doing wrong.
I tried another set of plugs to see if the other ones were fouled and no change. It was easier to start and would idle but at a very low rpm, >1K. I agree that I may be too rich at idle but I do not think that I would be too lean when I crack the throttle. But then I suck at jetting. Sometimes I should just ignore my logic. I may try swapping a few jets to see if anything changes. But the tapping/knocking sound still exists.
A buddy called me tonight, who used to built Fiat X19 motors, and he described the tapping sound as a diesel knock and had the problem of the wrist pins being loose in the rods. Did not check the pin-piston fit but they are the same pins I was using with the 75mm pistons without any problems so the pin-rod fit should be fine. From what I remember the pins were a tight fit in the pistons. I do have 2 sets of pins and may have switched them I do not remember...damn CRS (too many head injuries).
Oh well, since I am going to have to pull the cylinder to check the pins, I am going to put the 75mm pistons & cylinder back in with the head & cams that are installed now. Hopefully that combination will work. I am supposed to have another bottom end on the way, so I will build a second motor off the bike.
I need to have a running motor soon so I can make the Jennings track day on May 9th and this is probably the only weekend I have left to work on it.
Quote from: JamesGThis month's RRW magazine has a very good article on race engine building. When I read it I thought of your ordeal Darrell.
:(
I picked up the April issue of RRW but did not see an article about engine building. Was it in the Feb or May issue?
Quote from: Bob BroussardI have a air/fuel ratio meter. I installed an oxygen sensor in the exhaust.
Is that a junkyard O2 sensor off a car? That would speed the jetting process nicely.
The knocking sound has been eliminated. The pistons where hitting the head. With such a high dome, the pistons were tapping the rim of the head cavity. A little grinding on the head and all is good. Grinded some off the pistons as well to allow for plug clearance. The copper washer were not sealing all that well.
I have not changed the jets yet so it only idles. Adjusting the air screws helped in starting. It still dies when I open the throttle. I will increase the mains and hope it helps.
Its the may issue, Part of the AOD/NOTB articles; "How to go racing".
Its not super in depth, more suggestions and tips on race prep and engine assembly.
Quote from: JamesGIts the may issue, Part of the AOD/NOTB articles; "How to go racing".
Its not super in depth, more suggestions and tips on race prep and engine assembly.
They did not have the May issue yet...maybe this week.
An update on the motor upgrade (or degrade in this case)......
I am getting confused and really frustrated....I put the 500 cylinder back in with the milled & ported head, megacycle cams & jetted with 147.5/40/3turns (the same jetting as before with the 500 and stock head & megacycle cams). The bike will "run" with a low rough idle, like the timing is off. Open the throttle and no real change in rpm's. The carb slides do not lift with the twisting of the throttle. I checked the compression and vacuum (by cover the carb & plug holes with my hand & finger) and there seems to be plenty of both. The valves seat fine. Good spark. What am I missing?
:x :x :x :x :x
Dang this is frustrating....thinking about swapping heads and put the stock head with the megacycle cams since I had it running with this setup before. I never had the bike running with the milled head.
Any other suggestions or advise that I may be overlooking?
:dunno:
You using an Advancer on it? sure your Cams are set right ?(pref using degree wheel and dial indicator) there should always be a change when you open throttle, slides moving or not. you useing stock Carbs?
The carbs are stock and has a V&H ignition advancer. I keep double checking the cams and they are correct.
Are you installing the cams/setting timing with the V&H rotor on? I never trusted the timing marks on those rotors so always put a stock one to do the cams.
The only thing I can think of would be off timing, unless you had a massive cylinder leakage somehow (you did remember to put a head gasket on right ;) )?
I am setting the timing with the V&H advancer. I can swap rotors to verify the settings. It does feel like the timing is off but I can not figure out where/how. Yes, I do have a head gasket.
Are these the megacycle cams you are using? Have they had the sprockets slotted and moved?
They are megacycle cams and the sprockets have been slotted and moved. One thing I did do before taking anything apart, is marking the cams and rotor, when the cams are not pushing down on the valves, with a mark to help with reinstalling everything. I then check the timing according to the service manual.
Darn, I was hoping to get the cookie! :lol:
I donno man, Before I mangled mine... I had a lot of trouble getting the timing right with the MC cams. It was like they would always be one tooth/chain link back or forward and it would run like crap. I spent many hours at TGPR one weekend rearranging the cams before I finally got them right.
What I finally discovered thru serindipity (laziness) was that by leaving the chain tensioner in and letting it put tension on the chain, it keeps the sprockets more lined up and prevents them from slipping as you tighten down the holders.
Adjusting the cams? Are you referring to just moving the chain a tooth front or back on the cams? Were you adjusting the degree of the sprocket on the cams?
I know the factory alingment marks on the cams are not 100% accurate since they have been degreed.
I have been rereading my diary here. This is what I have come up with...
500 cylinder with stock head & MC cams - ran fine, pre-rebuild condition
555 cylinder with stock head & MC cams - ran with throttle response but w/ clearance issues
555 cylinder with milled head & MC cams - runs with rough idle & no throttle response
500 cylinder with milled head & MC cams - runs with rough idle & no throttle response
I do not understand how, what or why but the only common item related to the problmes is the milled head. I will be swaping heads later in the week.
BTW...what thickness copper gasket should I get? I am going to order one for the 555 for when I try installing it, again.
Consider the fact that you may be moving a lot more air because of the increased displacement. More airflow through the same size passages means a (more velocity) stronger vaccuum signal at the venturi which will pull more fuel through the same size jet.
So a smaller jet size may actually be needed.
This is sort of common in car motors where an inefficient motor will need more "jet" to cover up a velocity problem than a better put together motor will. (usually a person is over-camming).
I am unsure of this term but is this related to BSFC? (Brake Specific Fuel Consumption).
Maybe some SAE guys can chime in?
Shane
306 N2O Pinto
ps. I mentioned over-camming but I truly don't believe in such a thing. I believe in my heart that there is no such thing as too much cam, just not enough motor.