kpke Thrasher Engine Rebuild

[kobra]

I was wondering, why did you go with ProX pistons over the forged Pro Lites?

[kpke]

Searching for a "local" shop to bore the cylinders I did not really find anything, well one place that was $$$. I was just about to send the parts away and decide to call Brian Turfrey. "Yes I can bore your cylinders" he answered. I wanted 64.75 Wisecos. I ran the 64.5 Wisecos quite hard for 8-9 years so that's why I want Wisecos. He was glad to do it but his recommendation was to stick with cast ART pistons over forged. He gave a lot of explanation, he knows his stuff extremely well, so I was fine with that. He is a one hour beautiful country drive from here so it was done. No shipping and tons of education was received during phone calls and visits to his home/shop. Did a shit ton of banshee forum reading and it's pretty much like what kind of oil do you use? Forged are better for some and cast are better for others. I reckon I won't know the difference either way.

I was wondering, why did you go with ProX pistons over the forged Pro Lites?

[kobra]

Yeah what I gathered is the forged can take more abuse but they also slap around a bit more when cold and are more sensitive to both warm-up and break-in. The cast fit tighter and are like what came in the bike.
I am also considering cast vs forged. The cast pistons are about 40% cheaper too.

[Evans Ward]

The tuner that bored my cylinders the last time uses Pro-X. I only have about 500-600 miles on mine but runs great!

[kpke]

OK. This has to be what the original "chattering" problem was. I think. I hope.

Somewhere earlier I posted the rear sprocket a bit chewed on the outside. I've been anxious to get the engine back in the bike so I could check sprocket alignment.

I improvised an alignment set up and the sprockets appear to be about a half inch off. Very strange because it did not appear that way to the naked eye. Also probably f'kd up a nice DID chain.

Any suggestions to get this right are appreciated because I need to buy an offset sprocket, new rear sprocket, and new longer chain ($$$ you know). I also mentioned earlier for better swingarm clearance I am going to go 17 on the front and 43 - 45 or so on the rear. Also want it to be geared down slightly. Current configuration is 16 and 39.

The 3/8 x 1 alu bar is clamped to the front sprocket. The string is clamped to the bar very close to the sprocket.




The rear wheel is a little crooked but I think as long as I measure the distance between the string and the piece of wood at the rear axle it should be what I need.

[kobra]

Wow, that's a really big misalignment. More than I expected.

Is there enough material to mill off the sprocket carrier? Maybe if you offset that 1/4" and the front sprocket 1/4", they will meet in the middle.

[Whymee]

Something is very very wrong with the chain alignment.

Granted the chain alignment is way off by your pictures. The bigger issue I see is the string does not run parallel with the rear sprocket, even though it is .5 inch or so off. Something is really amiss here.

Make sure that your rear axle and your swing arm are dead nuts parallel. There is only one way to do this (that I know of) correctly. Although it is quite involved, unless you have access to a lathe.

Center Drill both the swing arm and the rear axle bolt.



Use the contraption below (some fabrication needed) to make the rear axle parallel to the swing arm bolt by adjusting the axle bolt. Never assume the stock alignment marks are correct.





Once you have the bolts parallel, Clamp a piece of metal that is straight to the rear sprocket, much like you have done with the front sprocket. Even if the 2 pieces of metal do not point to each other, they should be parallel. The difference they are off is the amount of offset needed.

I hope I have explained the above procedure satisfactorily. if not, ask away!

[Redline Junkie]

Use the contraption below (some fabrication needed) to make the rear axle parallel to the swing arm bolt by adjusting the axle bolt. Never assume the stock alignment marks are correct.

I hope I have explained the above procedure satisfactorily. if not, ask away!

Nice Contraption, I will need to make one of those!

[kpke]

Yes, it's alot. Not sure what happened there. I’ll have to take credit for not properly setting it up and I doubt any damage has been done other than the chain and rear sprocket. Thinking back I ran the 18" FZR wheel for 3 or four tires, so different alignment with that setup, then switched to the SV 17" with the GS500 sprocket carrier. There was an additional more professional set of eyes and brain power there and things seemed to be ok. It looks like I started running this set up around Jan of '17. I looked at my notes and took lots of measurements when I did the SV conversion but nothing says I had the sprocket carrier machined down. Doesn't matter because the chain is nearly hitting the 150 tire. I suppose if I get say the 10mm offset sprocket it will give me more chain to tire clearance and then have 2mm shaved off the carrier.

Whymee, I appreciate your alignment setup but I don’t have machining capabilities here. I mentioned the rear wheel is skewed at the moment. Measuring the string gap at the center of the axle should give me the offset distance or very close regardless.

I’ll align the rear wheel (to the best of my abilities) and then mess with it more today. But I don’t think that measurement is going to change.

Thanks again for all the input. Hopefully others can learn from this.

[kpke]

This is what it looks like with 2 CS sprockets stacked up on the front plus the wood and a 1/4" bar on the rear.




I took the wheel off to verify if the carrier had been machined and it was not.




So the current configuration is 16 x 39 = 2.44 ratio

I've ordered

Fastfromthepast
Offset (10mm) Sprocket 17 Tooth 520 Chain Yamaha RZ350 $59

Ebay
Vortex 528A-43 43 T 520 Aluminum Rear Sprocket Silver $57.75

I wanted a steel rear sprocket but could not find a 43T.

New configuration 17 x 43 = 2.53 ratio


I emailed and spoke to Sprocket Specialists to see if they have or can make 43T in steel. No, they can do alu for $75.

I could have went with a 16T offset and a 41T steel rear (16 x 41 = 2.56 ratio) but really want the chain further up off of the swingarm.

Once I get the new sprockets mounted I can do final alignment and have the GS500 hub machined down. The offset front will move the chain further away from the tire so there should be plenty of room to go back the other way on the hub. Another benefit (maybe) is I may be able to run a 160 rear tire. I just happen to have a brand new one in stock.

Still waiting on the Fox Shock to rebuilt and returned.

[kpke]

A few more parts have been installed.

[kobra]

Looking good!

With regards to gear ratios, seems like a good choice. I learned something recently called "hunting tooth syndrome" where you should always avoid a gear ratio where one gear is a multiple of the other. For example a 15/45 or 16/48. This causes the same teeth to contact in the same place on the chain every revolution and develop rhythmic/uneven wear patterns. Easier to visualize on a gear mesh but also applies to chain and belt drive.

[kpke]

Isn't that interesting. I guess I got lucky with

New configuration 17 x 43 = 2.53 ratio

[kpke]

Some updates with additional verbiage (for me) due to SIP and a little extra time.

Earlier in the week I started on the switchgear. The ones on the top came off of this bike and they work fine albeit being cracked, smashed, and ground down a bit. I thought about getting the rotten bondo out and attempt a restore on the ground down one and epoxy the cracked one, but I found the set below in a parts bin so…



The cracked throttle side of the unit from the bike.



Bringing some red back to the kill switch.



The inside of the left side unit from the parts bin.



Yuk. I’ll be using the guts from the working assemblies off the bike and the housings from the parts bin assemblies.





More to come.

[kpke]

The last wood oven project was so successful I decided to improve on the design. I had recently emptied this blue bin and was trying to figure out how to repurpose it. How about making it in to an oven. Can it survive the heat from the HF heat gun??? We’ll see.

So it’s all set up and running. But this revision did not last long. First that meat thermometer had to be installed upside down. Not a big deal.



Eh oh. The hole I made was just big enough for the nozzle to fit through and had a bit of a melt beginning.



After much thought and engineering and CAD drawing I had to go to the machine shop and fire up some of the equipment. I programmed the rotozip machining tool to open the hole up. And machined a wood collar for the nozzle to fit in to.



This revision worked better. The oven was spun around correcting the upside down thermometer problem.



It quickly heated up on low. I monitored closely the machine as it heated up. I was very concerned about a nuclear meltdown of the plastic material. That was the reason for setting it on cardboard to begin with, just in case it melted down.





At this time, I shut it down to make more improvements. After running it on high for a bit the back wall and sides were getting very hot. I made a wood plenum so that the blast of hot air would hit the back wood piece and flow back to the painted parts and not hit the back wall directly.



I ran a few cycles with these improvements and it seemed to work OK. BTW, when the COVID goes away I will search for a free or cheap house oven. I would then be powder coating this stuff rather than painting. This unit will then go up for sale. I am accepting bids now. I think I got it to register up to about 240 or so. With the thermometer down at the bottom I am thinking it was a bit warmer up toward the top.



Remember to start bidding soon.