billet head- very nice!

That'll be a real nice bike. Very much like the last one i built for my son. The 21in frame is my favorite. so much room makes everything fit so much easier. The roadmaster I just built had to use an offset intake , glad I didnt chuck the one that came with my Cns carb! Surprisingly the small frame is comfortable- I think the neck and bars give it a bigger feel. Anyways good luck with your build !
ps my pk80 piston should be here by saturday!
 

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cool new piston im sure it will make all the difference it can only get better

ok so i know having a shorter bike is more comfortable especialy with nice tall handle bars so you dont always have to be leaning over thats why when i put this bike toghether i got lucky to find a long riser with a piviting head so i can raise or lower the handkle bar height greatly and also adjust angle of bars so with this i hope to get a nice comfort ride
 
bluenosegoat said:
Thanks Jim,
I did remove the head today, I just had to see the piston shape. It is domed but not as much as your picture shows! I have a pretty good eye ( with my glasses on) bein a finish carpenter/ cabinet maker for years and I'm 99.9% certain I have the .100 dome piston in my engine. The engine is also at least 9 months old- thats how long I've been waiting to get my hands on one of these heads! When I'm done here I'll be placing an order with pirate for the pk80 piston amongst other things. Thank you so much for the pictures!
Click to expand...

You're certainly welcome.

You're probably right about the piston...the dome is really noticeable. Once your PK piston arrives you will be able to make the final comparison based on the photos in the previous post.

Once you have installed the new piston and replaced the jug...there will be one final check...deck height.

You want the edge of the piston to be .020"-.030" down in the bore at T.D.C. as shown in the graphic below. The measurement must be taken from the edge of the piston to the deck...not the top of the crown.

Plasti-gauge is an excellent way to determine the clearance between the head and piston; if you can find some thick enough.

WildAlaskan:

Once you have removed your factory cylinder head from your new GT-5...It would be a good idea to make the same checks before installing the new head...i.e. piston crown & deck height.

Jim
 

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Thanks again for the information! So can I assume the deck hieght is measured with out the head gasket in place? I hope its alright because I dont want to mess with changing the transfer ports by moving the cylinder jug up or down. I would think if the height is to large (piston to far down) that I should be able to lap sand the top of the cylinder down to the proper measurement with out changing port timing. Ahhh so much fun!
 
i should be getting my kit today and all the accesaries nut im thinking should i break in my motor before i install the head and expansion chAmber i plan on cleaning up the ports right off but i dont think i will be messing with widening them or lowering them till i find out howss it running
 
I wouldnt think it would make a lot of difference if the all the extras were on right at start up. I cant see what it would hurt but thats a real good question! I would think the pipe would actually help since it will be helping the engine "breathe" the way it should but then again its going to have a lot more power than plain stock so more frictional force on all moving parts.
I can only speak for my self but I would run for a week or so then I know just looking at all that cool stuff..... well I dont think I would make it a week!!!!
I fully agree with an adjustable stem. I was riding my sons bike one day and realized I wasnt so "leaned" over and therefore much more comfortable! I did notice since i put the new stem on my bike though that i can not ride as aggresively in the more upright posistion- nice that I can adjust it for my riding situation and might be good! I dont want to ever crash again at 35+ in shorts and a t shirt on chewed up asphault in 115 degree weather!
I cant wait for the piston to show up and I'm also hoping your build goes smoothly to hear about your performance with all the cool stuff! Maybe ask Norm about the break in period ? Any way I have some custom exhaust work to attend too! (finally found a 3/4 bender at a pawn shop for cheap!)
 
I was just taking off the head on one of my new engines to lap sand it and the jug and figured while the piston is just sitting there I would try to measure the crown. I made a little square with a notch for the piston rings to clear and with my little slide caliper was able to measure the approximate crown of the piston at the pistons shoulder. The two engines on my bench now are from BGF Z80S's and at least this one measures a bit over 5/32 = a little over .156 so it is the piston shape I'm looking for. Its not by any means the most accurate way to measure these things but you can really tell the difference between 3/32 (.093) and 5/332 (.156) so I'm sure this is the larger or more crowned piston. Guess this engine will be getting a billet head and go into my stretch cruiser for exhaust fitting! The other engine is looking for a home.
In the morning I will check out the deck hieght before I put the head on. Sorry son no billet head for you yet!!!!!( He wont notice- 17 and found him a girl friend- so much for father son time!)
pics - my crude 1min square- it is square though! just trying to hold it the engine and the cell camera at the same time! the other is the big difference from 3/32- 5/32
 

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So I got the piston from Pirate cycles (fast as usual, love the little packs of candy!) to get my engine taken apart and find out maybe my eye isnt as good as I thought! The pistons are the same! Owell so the new piston went in anyway but I did find the deck hiegth was way to much! I know you might not think this a good idea but there was so much material to take off the cylinder top that sanding it on glass would take forever and a day so I pluged in the belt sander. The belt sander worked very well! Kinda scary but it worked great! Then did the final lap sanding on glass to make sure the surface is flat. I dont have a good way to measure the deck hiegth but I know it was twice what it should be according to Jims posts. I think I have it down in the .03 range now- was afraid to take off to much material and I had to make my own base gasket which is just a touch thiner than the stock gasket. So anyhow got it all put back together (and got some real head nuts- ditch the acorn nuts!) and man I tell you!!!!! Now I have the performance gain I was looking for! Not to much more difficult to kick over but I can definatly tell the compression increase, glad I have the HD shift kit! Once running and warmed up I went over to the AT&T facilties parking lot for a test and when I gassed it over a speed bump the front tire came up into a wheelie!!! I was smiling! The bottom end torque is much improved and with the shift kit you get that power in every gear. So now I am happy with the performance of my engine. The shift kit, pipe, intake, carb and head are all doin what they are supposed to -- make me smile and get bugs in my teeth!
 
awesome thats great so you only had to adjust the height between piton and head

thats a concern for me on my new engine before i completly stripped down i took the head off and the piston at the lowest position wasnt clearing the transfer ports and the intake with piston at hightest position has a little it could go up

so i think i have to move the jug up so the transfer points are level with piston crown at lowest piont this will in tern clear the intake from piston skirt at highest position

and if i do that i will have to sand down the head to fit
 
At the end of your post you said " sand down the head", dont sand the head! sand down the top of the cylinder! (probably just a typo)
I have never messed with the transfer ports timing. I know the new base gasket I made is just a hair thinner than the stock one, but the material will not compress as much so maybe equals out. I've been leary on messing with the engines timing. I was surprised to find my engine's transfer ports runner down into the crank case are all smoothed out! All my other engines I have to take a dremel to them to take out all the sharp edges to help the "flow".
The belt sander worked out very well though. I can put it upside down on the bench and lock the trigger so I have both hands free to work the cylinder. I was just very careful not to put to much presure on it (if you know belt sanders they can take off a huge amount of material very quickly if your not careful!!). I basically had to eye the deck height. Like Jim said between .02 and .03 . .03 is just about 1/32 so I set my slide caliper to that so I could compare to the cylinder. I must be real close. And like i said what a difference! I picked up my daughter from school today on the bike and with her wieght and all the bike definately has more torque. I was able to cruise comfortable in 5th gear at 20mph just above an idle- nice and quiet so we could talk about her day. I'm gonna say I'm done with this engine. Very happy with it. .crt.
 
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sorry man i meant sand down the cylinder i will probly use a peice of glass cause i dont have a belt sander but i have used them before and the hey is let the belt do the work just let gravity exert all the pressure you need but any way i am strapped for cash so i cant afford the dremmel bits i wanted the gaskit material i need bearing grease sand paper engine enamel wiries for lighting system batery well u get the picture its a work in progress
 
I hear ya on the expense of all the little things! This Mountain bike has been an 11 month project and I would hate to add up all the little things it took!
I just used the belt sander because I can be impatient at times! It will take some time and elbow grease to lap sand on glass but well worth it to get the deck hiegth right! For Dremel bits sometimes sears has real good deals on them- I wont pay full price just because the package says Dremel but I have used bits from Harbor frieght Tools and they are okay, dont last as long but they do work. Also check on ebay for bits- I buy a lot of my 3/4 shank router bits on there and save a lot of money! (some can be upwards of 75 bucks!). I imagine you might already have it but I got some gasket making material from Auto Zone- was like 6 bucks for 4 sq feet and is really nice stuff- fuel resistant and cuts very nice with scissors and a razor blade- great for the base gasket and intakes- I even got away with it on the exhaust! so much cheaper and Sick Bike Parts has templates you can download.
I'm curious to hear how your engine build goes, have fun with it!
 
thanks man i will have fun it is on hold in a box right now but its still being built in my mind

whats the top speed you get and average speed?
 
I havent really checked out just how fast it will go. Before the billet head I've had the bike up to 39mph on flat ground and thats plenty for me! Right now with the head all done I can cruise at 32mph very easily and it pulls pretty hard from that speed in 5th gear and has plenty to go into 6th. I might take it out sunday morning on the way to church and open it up to see what the top speed might be. I have a 7sp cassette and the shift kit stock gears. I would like to get a slightly lower first gear on my cassette but I like the fact that I can cruise 20-25 at very low rpm's so its very quiet. With the heads increased compression you know it though when you get on it! The sound is sweet out the sbp pipe! Got the ping to it once again but its not quiet by any means when you are on the throttle. So basically its just what i wanted. I dont "need" the power but sure is nice to have it on tap. The bike reminds me of my yamaha yz80 back in the early 80's!
 
sorry about late response i was out of town

39 before a upgraded head sounds fast enough but im sure it would go at least 45 now

im gonna have a 8 speed cassete on mine and i expect to top out at 45

i know its fast enough i dont need the extra power but why not for me its all about getting up to speed fast i wanna beat those cars off the line that would give me a huge grin even when they pass me up

i also want to have a reasonable cruising speed with a lower sound level so these upgrades should give me what im looking for

im just need to go backto work now so i can afford a shift kit
 
Sounds like we are after the same thing! The shift kit was the most expensive single item on my bike but well worth the money. I estimate about 2,000 miles on mine- usually pulling a trailer- and it has held up very nicely. I estimate with the bike, trailer and my daughter and some grocery items to be about 300lbs+. I had to replace the chain to the freewheel about 100 miles ago but other than that just oil the freewheel and ride! (When you get your shift kit order the freewheel oil also).
 
free wheel oil huh never thought of that
i will thanks

but yeah the shift kit is definetly a slick idea maybe next time i will sorta make my own maybe but im gonna buy this one first

so what shift kit did you buy was it the hd shifter kit or the deluxe hd shifter kit

it seems like for 40 extra bucks i already got a chain breaker and a crank removal tool i have acces to but i have heard bad reviews for the dual brake lever used with v brakes

so that only leavs the extra sprocket well i could buy to of them and a bottom bracket tool for the same price

so i think ill go for the hd kit
 
I got the hd kit. Like you I already had some of the tools and I usually make my own dual brake levers. I do however use that brake lever with bikes I build and sell and it works great with every brake system I've used them with- all but disc brakes so far. The brake lever isnt by any means very heavy duty- its no diacomp or anything but it does work well. The other thing I'm not sure is included in the deluxe kit is the twist shifter. It is a must! I tried with "click shifters and thumb shifters and niether of those worked to well. The twist shifter is the ticket! I ended up buying a complete bike for 15 bucks that had the shifter so got the extra parts of a complete bike to boot!
 
http://www.cyclexpress.co.uk/dbimgs/acera.jpg

this is the shifter im gonna try out i already have one but black

the way i am looking at it if i have a twist grip throttle i would throttle down to shift up that would move my hand foward and to up shift pull the top lever back so i could pull that and throttle up when i wanna shift

i have played with this and i beleive it will work well if im not happy with it i can change things around

i might also try out using the brake handle as throttle that might be smoother i currently have a brake lever for throtthe and it works out well i would like to have a dual brake lver but i havent had any problems with havine two levers on each handle
 
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