big bore cooling?

[eliteguy50]

I am thinking about big boring a dio but I don't know about cooling. Do I have to buy a special oversized shroud and block cover or make my own to accomodate the bbk size with the air cooling? I know I will have to upjet but that can't handle all the cooling.

I was thinking about chopchop's kit because it is the cheapest and this would just be a bbk plus gears for a fun beater.

http://cgi.ebay.com/ebaymotors/Honda-SA ... leQ5fParts

[808BMW]

I have that kit, the stock fan shroud fits. I just trimmed around the spark plug because it fits tight.
Upjetting will pretty much take care of the cooling, I'd recommend a temp gauge so you know whats going on.

[burnt_toast]

I am thinking about big boring a dio but I don't know about cooling. Do I have to buy a special oversized shroud and block cover or make my own to accomodate the bbk size with the air cooling? I know I will have to upjet but that can't handle all the cooling.

I was thinking about chopchop's kit because it is the cheapest and this would just be a bbk plus gears for a fun beater.

http://cgi.ebay.com/ebaymotors/Honda-SA ... leQ5fParts

stock cooling would be fine for that, but keep in mind you will have to port boost port

notice the base gasket for that kit and look at your elite boost port. the improper flow unported will cause easy overheating

better off buying taiwan 47mm dio bore, bolt on fit and plenty for a beater

[eliteguy50]

better off buying taiwan 47mm dio bore, bolt on fit and plenty for a beater

where do I find that?
my theory was that chopchops kit would still be cheaper than the other ebay kits are...

[burnt_toast]

better off buying taiwan 47mm dio bore, bolt on fit and plenty for a beater

where do I find that?
my theory was that chopchops kit would still be cheaper than the other ebay kits are...

yeah it'll be cheaper but wont work right without porting boost port on your cases

alum cyl from daywot isnt far off and no worries about cooling. you can find some guys selling used bore in hawaii forums and craigslist pretty cheap, just gotta get em to ship

[808BMW]

I'm running a 50mm bore, and I know 3 guys running a 51mm, all of us with stock boost ports.

[Lunytune]

I finished installing Tazland's 50mm on the 4th, and yes Toast, I did port and polish the back portion. It's really simple. Marc sends headless studs for alignment. I put the gasket on, put the studs in to hold it, and marked the area with a laundry marker. Then grind it out and smooth it up. I laid duct tape in the bottom to catch the cuttings, and mop up was actually pretty easy.

808BMW, I'm glad to know I'm not the only one having problems with the plug wire. I thought I had distorted the fan shroud.

I put the #100 jet in, that Marc sends with the kit. I mixed extra oil in the tank. I've been running it a little each day, no WOT or long drives. I pulled the plug today and it was Swiss Chocolate brown. Plug had a soft cake on it, I assume from the rich oil mix.

I don't know how the 47mm kit runs, or the Ruinia (sp?) 51mm, but I can say this one is going to be a screamer. I crunched the numbers and it puts it up to a 80cc. As far as heat, I don't have a temp gauge and can only go by the plug, but so far so good on that.

For $87, it's pretty hard to beat. I paid close to $200 for daywot's Polini for my SA50.

[808BMW]

The plug gets moved a bit back on the bigger bore, so clearancing the shroud is common.
So you matched your boost port without splitting the cases?
I left mine totally stock because I have a 47mm polini bore to go on, I just don't have a piston yet. The boost port on this 50mm kit is much bigger than a 47mm, so I didn't want to overbore it.

[Lunytune]

So you matched your boost port without splitting the cases?

I didn't care to go into the bottom end and split the case. I was very careful to layer duct tape in to catch all the dust, and protect the bottom end. Once finished, I took a rag soaked with a light weight oil mixture called "Ed's Red", and it picked up the aluminum dust real well.

I didn't go "down" very deep, just tapered down from the laundry marker black. Once you get so far, there is not enough meat in the case to grind. I didn't want to weaken the case. But I figured the taper and polish accomplished the task.

I'm still breaking it in, still working on first tank of gas. We went out last night for first long run, 5 miles, and I wrapped, coasted, wrapped, coasted... Wife thought I was having trouble keeping up with her Polini. Nope, just taking it easy.

Since this is my first experience at porting and a big bore on a Dio, I don't know what I gained in the porting. Have you done a before and after with nothing but the porting to observe the difference? All I know is when my SIL and friend walked in while I was doing it, he got a silly grin on his face. He used to race 2 stroker cycles. That was before marriage and my daughter won't let him have one now.

[Arnadanoob]

I have that kit, the stock fan shroud fits. I just trimmed around the spark plug because it fits tight.
Upjetting will pretty much take care of the cooling, I'd recommend a temp gauge so you know whats going on.

Exactly as 808BMW has said, the stock fan shroud will fit but you will need to grind the hole in the shroud a bit where the spark plug goes because your new bore kit will position the spark plug further back, this is nothing special as all bore kit upgrades like this will require at least this small modification.

One thing a lot of folks seem to misunderstand is that the fan (air cooling) doesn't do the bulk of the cooling for the engine. The fuel (jetting) is what's doing the majority of the cooling. The fan shroud and fan is there to prevent the temps from running away while the fuel jetting is there to help keep things at a stable sustained temp during operation. Get a CHT gauge and tune the bike so that the avg temps stay around 250-300F.

[burnt_toast]

I'm running a 50mm bore, and I know 3 guys running a 51mm, all of us with stock boost ports.

not saying you cant, as i know many others who run this combo as well.

but you'd have to agree with boost port matching you have better mix charge delivery and as arnadanoob said, since the fuel is what actually does the cooling, this would translate to better overall cooling.

[Lunytune]

but you'd have to agree with boost port matching you have better mix charge delivery and as arnadanoob said, since the fuel is what actually does the cooling, this would translate to better overall cooling.

So then is cooling the primary purpose of boost port matching? I know in the 4 stroke racing world, port and polish on intake is part and parcel to more fuel and power, apart from cooling, and on exhaust side to get gasses out quicker with less back pressure.

[Arnadanoob]

The boost port is the port(s) located opposite of the exhaust port and inline with the intake port which helps with scavenging. Cooling is just 1 small part of the scavenging process. Port matching allows the scavenging process to occur smoothly without turbulence. When a smaller port encounters a larger port, the effect that occurs is that a higher pressure area (small port) loses gas velocity when it encounters a port of a larger size. An engine is nothing more than a fancy air pump, the more air that flows through it develops more power, this part is no different from a 4 stroke or 2 stroke engine. When gas loses speed (velocity) you lose power.

[wikked_spree57]

so if i pick up tazland's 50mm kit, am i going to need to do any porting or can I run it on my block as it is? i did notice that the stock boost port is pretty small.

[Lunytune]

About all I can say is, I don't regret what I did. It's not that hard with a dremel, except you need to finish it off with a fine grade of sandpaper or emory cloth. This AF16E/overbore screams. I didn't port boost my SA50/AF05E when I put the Polini on, but am thinking about tearing back down to do it. The Polini gave an increase in power, but I think porting might add more.

And yes, there is a considerable difference between the stock port and the upgrade on the Polini and the Tazland 50mm. If you don't relieve it, you're only going to get what the stock port will give you.