New engine build progress

[mapbike]

I've had this engine since 2010 just sitting in a box in pieces, I didn't want to build it up until I had the crank I wanted in it and the jug I wanted to use on it and also until I had time to do the port work like I wanted it.

Its coming together now, I got the case cleaned up good, got the rough rolling china bearing out of it and got the new butter smooth 6202 Nachi Japanese main bearings installed, I polished the main journal areas on the crank so that the bearings are tight but press onto crank without a huge amount of force, got new crank seals installed, adjusted spanner nut on clutch spring to give the clutch a tighter hold before coating the spring well with a high quality high tack moly grease.

It will take multiple post here to share all the pix, but I just wanted to show the lower as it was coming together and show the transfers shape and size based on what we see with most all of the engines we're seeing now.

The crank in this engine is a 40mm stroke GenIV crank that I got from Duane/dax last year, very true spinning crank, by far the nicest looking cranks I've seen hands down.

I will need to make some woodruff keys for the crank tomorrow, I have the ones that came out of the old crank that was in this engine but they're to wide for this crank and I don't want to shave them down because then I wont have keys for the other crank which I think is a fairly good one also, but it's a half breed type with a 38mm stroke and the 110mm rod.

So enough with the jabber, here are some pix of the engine lower up to how it sits now.

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[mapbike]

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[mapbike]

I also wanted to add some pix and a brief explanation of how I install new seals after the crank is in the engine, it can be a very big pain in the backside and you can easily ruin the new seals if care isn't taken, here is a method that makes it easy, quick and will prevent damage to new seals.

I didn't think to share this until I had already installed my seals, but i thought this may be helpful to someone who may need to replace the seals at some point.

I guess I should have given a bit more detail but i'll try to explain the best I can what I used and how I made the simple tool for the job.

First get some oil, 2 smoker, 3in1 oil, regular engine oil....etc, you don't want the seal or crank to be dry when installing the seal.

The special dinky little tool/sleeve/tube you see in the pix is a piece of thin .008" aluminum flashing, shim type material, I took a long 3/8 drive ratchet extension and wrapped the aluminum around it just until it overlapped, made note of the place where it would but up if it was cut and then slid it off of the extension and cut it with scissors.

Then I slid the aluminum tube over the crankshaft where the seal will seat, the crank dia is larger than the tube when it expands on that end to fit over crank but not much and not enough to hurt a thing, then I just lift the tube up off the crank, smear a little oil on the outside of the tube, slide the new seal down about half way, then put the tube back over the crank like it was before and slowly slide the seal down the tube until it starts pressing into the engine case a little, I then take the same 3/8 ratchet extension and use the square end to gently tap around outer edge of seal and work it into the case evenly about half way, the just pull the aluminum tube out and finish tapping the seal down into place.

Another thing I will add here is that I have an idea about something else that might work instead of using the aluminum flashing, but until I try it to see if it will work I wont say anything about it here yet but I will post the info here if it does work when I look into it tomorrow.

Anyway, this "breif" post got way beyond brief....lol but here are the pix and hopefully this will help someone at some point get their seals changed with damaging the new ones and causing the spring the is behind the seal lip to pop out between seal and main bearing.

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[bluegoatwoods]

"Rolling" the seal.........Aaaarrrggghh!

For many years I was in a business that involved my installing oil seals. It was difficult for a newbie, of course, to install them without rolling them. But even after I became pretty good at it, there would still be individual units that would be so troublesome about it that there were times that I'd nearly tear my hair out.

But, anyway, nice job on that installation tool.

 

[allen standley]

Thanks Map Good StuFF!

 

[mapbike]

Thanks Map Good StuFF!

you're welcome Allen, I know some on here could care less about pix of the build Im working on, but I know I always enjoy seeing what others are doing with an engine or their bike so I just figured Id put some pix up as this one comes together and share the simple rcountry boy engineering I use to i stall my seals without rolling them back and causing the spring to pop out or damage them in some other way.
I learn new things from members on here all the time and try to share things I think may help someone else.

Ill be adding more pix here as Im able to work on this engine and get it together, honey doo's and basically some need to get done stuff around the place is on the agenda for today or I would be doing more with the engine, its possible I could get a little time for it later on but Im not sure yet..... working like a dog out back of the chicken house now and the brush cutting, and shoveling leaves, dirt and briars is working some fat off along with some energy.....lol

 

[allen standley]

Darn snowing like crazy here. You do what you gotta do... Here I pay attention with appreciation.

 

[Eric2.0]

Thanks, Map. Nice to see how these look inside.

BTW I got mine started.... it was a good day.

 

[mapbike]

Thanks, Map. Nice to see how these look inside.

BTW I got mine started.... it was a good day.

Thats great Eric, always nice to hear it run for the first time.

 

[frank66]

mapbike listen. currently you cannot trace a custom headgasket or port the transfers without aggrivation.

pocketbikes do not have an inside transfer tunnel.

i have used a hacksaw to score and cutout 70 percent of the inside transfer tunnel. then crack it off. it took 5 minutes.

then smooth and raise the port height. and trace a head gasket.

lots of room for tools and hands this way.

 

[mapbike]

mapbike listen. currently you cannot trace a custom headgasket or port the transfers without aggrivation.

pocketbikes do not have an inside transfer tunnel.

i have used a hacksaw to score and cutout 70 percent of the inside transfer tunnel. then crack it off. it took 5 minutes.

then smooth and raise the port height. and trace a head gasket.

lots of room for tools and hands this way.

Im not sure I know what you're saying here.

who's needing to "trace a head gasket" ?

explain what you're talking about doing pif you dont mind, I dont need transfer raised on the jug Im using on this engine since they are almost completely open when piston is at BDC, exhaust port is almost completely open at BDC and actually intake is about 90-95% open at TDC so Im happy with how the ports are positioned .

 

[frank66]

im just trying to help. you did a nice job on the block anyway.

you probly dont need a custom gasket but the grubees could use a thinner base gasket.

if you look at theons pictures of his pocket bike cylinders you will see no inside transfer tunnel at all. like this it is easy to raise the ports with nothing in the way. it would match your case perfectly/ thats why i brought it up.

its not hard to do. i know its been done b4 with mixed results maybe.

looking good guy. l8r

 

[mapbike]

im just trying to help. you did a nice job on the block anyway.

you probly dont need a custom gasket but the grubees could use a thinner base gasket.

if you look at theons pictures of his pocket bike cylinders

You said head gasket... thats what threw me off.

I make my own base gaskets, intake gaskets and have also made several aluminum head gaskets, not hard to do at all, just takes a little time and sa sharp exacto knife.

I do have some nice thick premade base gaskets and I've already got one reshaped to work perfectly with the transfer areas of the case and me jug is perfectly port matched to the case transfers and the gasket, this is very easy to do with the right tools and some patience.

Thanks for the input though.

 

[mapbike]

As far as what I've seen with the GT5 engines they actually will benefit from a thicker gasket and the the deck needs to be shaved/milled down to get the to have better high rpm power and keep the compression at an ideal level.

 

[frank66]

forget about the gaskets. let me start over by simply saying the transfers would be alot easier to perfect if the inside transfer tunnel was cut completly away like the piston port pocketbikes.

 

[mapbike]

forget about the gaskets. let me start over by simply saying the transfers would be alot easier to perfect if the inside transfer tunnel was cut completly away like the piston port pocketbikes.

Are you talking about cutting the cylinder wall out all the way down the Tranfer tunnel in the jug?

If so I know whT you meen now, Im not familiar with the piston port pocketbike engines so I didnt get wha5 you were saying.

 

[frank66]

yea. im sure it has its pros AND cons. it would look exactly like your block. two peas in a pod im waiting a month so i can do lots of before and after test drives. cylinders are not expensive.

you did a great job on the block so i wanted to say something.

 

[mapbike]

yea. im sure it has its pros AND cons. it would look exactly like your block. two peas in a pod im waiting a month so i can do lots of before and after test drives. cylinders are not expensive.

you did a great job on the block so i wanted to say something.

Thank you, sorry it took me a few tries to figure out wthe point you were making...

Its been a couple or so years back but someone did the mod you're speaking of, I think there was some debate about it here, but I think who ever it was that had done it said it worked, Im not sure if any performance improvements were realized or not.

as far as I know the builders that are getting the most power and top speeds from their engines arent doing that mod, but there may be some gain to be had.

Im sure myself and others here will be interested to know what your results are when you decide to give it a try.

 

[Davezilla]

Yes, open transfers has been tried and experimented with and the end result waas a Very strong top end but the bottom end was so sluggish it needed to be pedal assisted to at least 15 mph before it would accelerate on it's own. If you got a spare engine and a few spare jugs you can experiment with open transfers but be sure you got bigger rear sprocket if you plan on using it for anything other than racing... The mod works great on top but kills bottom end performance.

What would give a much better "happy medium" would be to leave the transfers closed except for the stock openings, knife edge the openings at the base and at the bottom of the port so there's no turbulance from the bottom of the transfer opening. The incoming charge will still hit the piston on it's way down but rounding off the edge of the piston crown at the transfer openings will smooth the flow back out. The outer walls on the transfer tunnel can be opened up pretty far and tapered to the width of the transfer openings for more velocity and also for better aiming of the rear of the port as long as the rear of the port isn't opened all the way up it can be aimed pretty well by cutting slightly into the outer tunnel wall and the rear tunnel wall.

 

[kevo]

Dave your exactly right! I've tried to cut the transfers open with OK results at high rpm but I lost everything at low rpm. My China girl will top out at 42mph with the transfer mods you speak of. Its really a balancing act to get both. Maybe with huge transfers and a Reid kit to help the low end.