How to soften rubber?

aardvark · Post by **aardvark** » Tue Mar 28, 2006 8:55 am

Believe it or not, I got the bastard on.

20 minutes with the heatgun sorted it out.

Stace · Post by **Stace** » Tue Mar 28, 2006 9:09 am

Jase, Send the carb over with Mark when he comes over and i'll spin a bit or the O/D for you, Just let me know what Dia you want and the size ECT of the retaining groove and i'll do it. Should only take about 30 Minutes.

Or just post it over, Postegae will probably be cheaper than paying someone else to do it.

aardvark · Post by **aardvark** » Tue Mar 28, 2006 9:48 am

Thanks Stace,

But it's all good. For now.

Stace · Post by **Stace** » Tue Mar 28, 2006 9:59 am

No worries, Let me know if you need it done.

ZZRCHIKKY · Post by **ZZRCHIKKY** » Tue Mar 28, 2006 10:20 am

duh, water boiling weater on da stove

Gosling1 · Post by **Gosling1** » Wed Mar 29, 2006 5:44 pm

ZZRCHIKKY wrote:duh, water boiling weater on da stove

won't work on reed-valve manifolds, the rubber is *way* too thick....

20min with a heat-gun??

bloody hell, surprised it didn't melt !!

good work, hope it stays together OK, and that you have the jetting correct .........

aardvark · Post by **aardvark** » Wed Mar 29, 2006 11:03 pm

Gosling1 wrote:20min with a heat-gun?? bloody hell, surprised it didn't melt !!

good work, hope it stays together OK, and that you have the jetting correct .........

20 minutes may have been a slight exageration. Probably closer to 10.

I hope it stays together ok as well. Seems to be pretty secure.

Have got no idea if this bastard will run. I have rebuilt the motor myself. My brother got the die-grinder onto the ports. The piston is a go-kart piston and 3mm taller than the standard one. Have lifted the cylinder and head by 3.1mm to get around the piston issue. The carby is a stock RG250 carby with standard jetting. I'm just gonna set the mixture screws to the middle and try to fire it up. If it doesn't work, I'll play with it and see what happens.

You havent heard about the problems I had trying to mount the engine to the frame and the hack job I've done getting it to fit. If you want to hear about it, I'm happy to tell the story and provide photos.

Stace · Post by **Stace** » Thu Mar 30, 2006 8:35 am

Better fill us in the Jase.

mike-s · Post by **mike-s** » Thu Mar 30, 2006 9:15 am

i'm all ready, fill us in.

aardvark · Post by **aardvark** » Mon Apr 03, 2006 10:12 pm

The bloody motor...

After having just rebuilt it, I decided it was time to fit it in the frame.

Put the first mounting bolt into place, swung the motor up and.... Damn, bloody second engine mount is all wrong. *sigh* As you can see in the pics below the bolt hole, which is cast into the engine case, was too long. Considerably so!

So, how to fix it? Out with the hacksaw.

I chopped the end of the bolt hole on the engine off and the sucker fit into place. I had to drill the holes in the frame out a little to get everything to line up, but it sorted the middle engine mount out.

The third and lowest of the engine mount on the frame didn't line up either. Turns out I have a H100A motor and a H100S frame, which are obviously not really that compatible. I had to take an angle grinder to the frame and remove a spacer from the frame, then redrill the bolt holes in the frame.

In the end, a rubber mallet and some elbow grease sorted it all out.

The bike is at the exhaust shop at the moment and the bloody thing should be completely together by the end of the month.

Gosling1 · Post by **Gosling1** » Mon Apr 03, 2006 10:26 pm

aardvark wrote:...Have got no idea if this bastard will run. I have rebuilt the motor myself. My brother got the die-grinder onto the ports. The piston is a go-kart piston and 3mm taller than the standard one. Have lifted the cylinder and head by 3.1mm to get around the piston issue. The carby is a stock RG250 carby with standard jetting. I'm just gonna set the mixture screws to the middle and try to fire it up. If it doesn't work, I'll play with it and see what happens:

OK, what you will also need to do (if you haven't already), is modify the inlet/transfer/exhaust ports, because by lifting the barrel 3.1mm (assume you have fitted an aluminium spacer plate between crankcase and barrel base..?), you will have also *severly* altered the (a) inlet timing, (b) exhaust timing, and (c) transfer port timing...........

I guess your brother may have altered all these to suit the new piston and port heights ??

Love your work with the engine mounts, this is why they are called 'Bucket' racers......

Keep the updates coming, its always good to see how these issues are dealt with ......

aardvark · Post by **aardvark** » Wed Apr 05, 2006 7:22 pm

Gos,

I'm not convinced that I need to chage the ports to suit the new piston.

Relativley, the ports will be in the same spot to the top of the piston.

I'll give it a go as is before messing with things.

Gosling1 · Post by **Gosling1** » Wed Apr 05, 2006 8:18 pm

aardvark wrote:Gos,

I'm not convinced that I need to chage the ports to suit the new piston.

Relativley, the ports will be in the same spot to the top of the piston.

I'll give it a go as is before messing with things.

OK, well give it a go, but your port timing will be way out......

Its not relative to the top of the piston at TDC, its relative to the number of degrees of crank rotation for opening and closing the ports......

the stock ports are timed to work with a certain number of degrees of crank rotation. Once you raise the barrell, you change the number of degrees of crank rotation for both the opening and closing of the ports.....

I have attached 2 pages from my 2-stroke 'Bible', and these explain the importance of correct port timing........sometimes a change of only 2-3deg in exhaust timing can make a bike unrideable.........or a rocketship

aardvark · Post by **aardvark** » Wed Apr 05, 2006 10:31 pm

I've read that book. Made my head hurt.

Jonno · Post by **Jonno** » Thu Apr 06, 2006 1:08 am

aardvark wrote:I've read that book. Made my head hurt.

welcome to engineering