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Junglejeff

Twin shock project

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Made the jug nicer to look at.Working on parts like these as I am waiting to get frame back from powdercoat.Spray bombed cylinder with engine paint.I don't powder cylinders as it holds in alot of heat.cases I am bringing to a friend's house to use his oven to powder cases in Satan black. My little 2 pizza oven will not fit cases and he has a old full size electric oven for bigger parts.Figure if my carb has a leak I don't have to worry about a leak messing up the black case with powder. 

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While I was messing with cylinder I smoothed out and port matched.transfer ports were pretty nasty and transfer ports were a little off time but not to bad.Going to figure out a way to mount my head in my old harbor freight lathe to mill down a bit.yami,s are known for crazy big sqish bands so will correct that if I find it,s a issue. 2 strokes jet so much cleaner with proper sqish.

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Turn a mandrel up with spark plug thread on it then wind the head on without removing the mandrel from the chuck, that gets the head running as true as possible. I altered a YZ490 head using this method & it worked well

I had thought about increasing the compression by removing some material from the gasket surface then reinstating the squish band but found having a fresh bore & piston kit improved the compression enough

The only work I did to the ports were done to the intake to allow a YZ85 V-Force reed block to fit, no polishing was done. The transfers were already quite well matched, the divider had been knife edged which is now considered to be counterproductive but I didn't bother changing that. You'll be surprised just how good a fresh TY250 motor is

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I replace the original head gasket with a thin aluminium one that I made from the original model, it does change the compression. I ran that for a while with no issue.

Guy

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14 hours ago, guy53 said:

I replace the original head gasket with a thin aluminium one that I made from the original model, it does change the compression. I ran that for a while with no issue.

Guy

Might go that way also.When I have motor together will check with solder to see were I am at.I checked out amazon and found I could get thin aluminum or copper plate cheap.

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16 hours ago, tony27 said:

Turn a mandrel up with spark plug thread on it then wind the head on without removing the mandrel from the chuck, that gets the head running as true as possible. I altered a YZ490 head using this method & it worked well

I had thought about increasing the compression by removing some material from the gasket surface then reinstating the squish band but found having a fresh bore & piston kit improved the compression enough

The only work I did to the ports were done to the intake to allow a YZ85 V-Force reed block to fit, no polishing was done. The transfers were already quite well matched, the divider had been knife edged which is now considered to be counterproductive but I didn't bother changing that. You'll be surprised just how good a fresh TY250 motor is

Well that sucks.I rounded the transfer split some.I am trying to keep bike smooth but have a little more kick.Fiqured shaving like a 3rd of flywheel weight off will give me a little more kick.Our club uses pretty modern sections compared to old days so want a little quicker hit.Never tried shaving a head like that but will if needed.Not sure my little harbor freight lathe has enough swing to fit it.

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Mine has no flywheel weight on it at all & it works quite well, the flywheel had the band removed before I got hold of the bike so I can't say how it changed things

Having a radius on the bottom of the transfer divider is what the top 2 stroke tuners reckon works best, wouldn't be something that would be noticeable on a lightly tuned trials motor

The event I got the bike running in time for last year is a 3 day event where twinshocks ride the same sections as the clubman classes but are scored seperately. It's always good to be able to compare the scores & work out how many of the new bikes have lost more marks, first day I lost 1 which was either the same or better than the top clubman, other days I don't remember apart from the scores were higher  

 

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I've also been riding my TY ( s ) without flywheel like Tony 27 for the last 10 years. I remember marking the first one I took off just in case I would not like the feeling, never bothered after that. Not all riders like the feeling, the Bultaco guys in particular.

Guy

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Flywheel effect is definitely a personal taste thing. I suggest you try riding it however it is now before making changes. It can be a pain trying to refit the steel band to a TY250 flywheel.

TY250 twinshocks have become fairly popular around here over the past 10 years so I've kept a flywheel with no band that I lend to people so they can try it on their bike before they do something to theirs that's hard to reverse.

I machine about 1/3 of the steel band away on my late model TY250 flywheels and have left my A model flywheel with the small band standard.

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To add to David's post, the effect of the modified flywheel is not only felt in acceleration, you also feel a difference when you shut the throttle down. I tested my bike with a B model flywheel ( extra heavy ) and one with no ring back to back on the same sections, riding in the parking lot was not convincing, but when you get in a tight section, than you feel the difference. I have to say that I use the clutch more with the '' no weight '' flywheel.

Guy

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I lost a transmission trust washer so have to wait for it before I assemble engine. Cleaned up the forks and brake plates and powdercoated with flex black.ordered new 803 tires from rocky Mountain. Going to put the new back tire on my GG and put the good used tire on TY.Just replaced front on GG so TY gets the new front.Received new chain and sprockets from tytrials.The gold dished rear sprocket looKS awesome. 

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Project looks to be coming along nicely. I'm interested in hearing how you like that OKO carb when you get it all back together!

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Project is coming along well.Ran into a issue with front wheel and left slider.Slider must have took a good hit at one time.fork jams up about 3" before it bottoms.I ordered a set of forks from a bone yard for 80 bucks to rob parts from.front spokes were froze up to bad.Even with heat and pb blaster they broke like glass.Ordered a stainless kit from speed and sport and it came in today.

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Really nice build on your TY Jeff. I think they are one of the better twin shock bikes with two things the Spanish bikes of the same year don,t have box stock,good brakes and clutch. I,m sure the finished bike will look and ride superb.

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Replaced left slider because original had some internal issues. Picked up a set of forks for parts off ebay for around 80 bucks.Now I have extra damping rods to experiment with.Installed magical springs and new seals.Starting to put bike together and looking good.Laced the front wheel up and went well.Was not thinking when I cut off old shock mounts in back.The seat bolts to backside of them so now have to fabricate another method to hold seat down.I don't like the seat and will change it up in future. Might go out to shop and weld a rear mount on mx 80 tank so I can do some body work on it.

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