Honda Gyro TG50M (1985)...lets make her faster?

Kenny_McCormic · Post by **Kenny_McCormic** » Wed Dec 10, 2008 4:20 pm

Port it out, build a pipe, make it scream!

Twilight · Post by **Twilight** » Wed Dec 10, 2008 6:26 pm

Working on a better rev and torque pipe right now. But as for porting. I would like to see how much is usable in the cylinder before tearing into it.

Kenny_McCormic · Post by **Kenny_McCormic** » Wed Dec 10, 2008 7:04 pm

Ring width off the top of the exhaust port is a good pretty well guaranteed not to be over kill. As for the transfers just clean up, knife edge any blades you find, cut some CF reeds.

Wheelman-111 · Post by **Wheelman-111** » Wed Dec 10, 2008 7:41 pm

Greetings:

Do cf reeds help midrange as much as top end power?

Starting new topic seeking answers to this Q.

Kenny_McCormic · Post by **Kenny_McCormic** » Wed Dec 10, 2008 7:44 pm

I think they help all over.

Twilight · Post by **Twilight** » Wed Dec 10, 2008 10:15 pm

Yeah im planning to clean the ports up, i know all cast cylinders have those sharp edges... blah.

I am hoping that mousewheels has some pics of the cylinder so I can see how much there is to work with and if its worth it.

mousewheels · Post by **mousewheels** » Thu Dec 11, 2008 4:35 am

Twilight,
I'll get photos for the Gyro cyl tomorrow - was busy tonight...

Here's reply to your earlier comments.

I have a theory too. After reading that I took my Gyro down a hill here in West Seattle (Roxbury), shut the engine off and let it roll as fast as it could. There is bogging at 37mph, I am guessing thats all the trans of these machines can take.

There's a freewheeling clutch inside the trans, not all of it has to rotate when coasting, it's loafing ;^). Rear tires at recommened 11psi are poor rolling resistance. And though low, the Gyro position is likely no better than a tuck on the dropped bars of a bicycle.

So, how much usable bore is there on these engines? Can they be bored at all?

I'd say its in the ballpark of a Spree. Keithw has a great thread on performance improvement of an 85 Spree. One of his tests is with a 3mm overbore piston. If I'm up to date with his work 3mm overbore did not give results desired, and Keithw swapped back in a stocker. Balance was one issue Keithw found.

Anyway - 2mm would get us around 55cc. There's import pistons on eBay International for the Honda Vision that should work. The seller has 2mm overbores - ask for part 935058. This item number is for a std 310084860330. I've got a pair of these - but been sitting for 1 1/2 years :^( Here's some links to an older threads for oversize pistons from other sources on this board. http://www.hondaspree.net/phpBB2/viewto ... c&start=15 http://www.hondaspree.net/phpBB2/viewto ... 18&start=0

Whats the chance of a 84 gyro engine fitting? I have a lead on one that if needed I will use as a base on my project.

The '84 engine should bolt up to the pivot mount. But there's little differences. First gear ratio is lower on the '85/86. Port timing is different, with the '85/86 opening sooner and longer. Internally, the clutches are different too. The '84 have more mass, I think they engage sooner. The brake cable bosses are different, the '85 are larger diameter, your cables won't fit up correctly with an '84 engine. There's some bolt thread differences for the bolts that mount the exhaust and a few other minor items. So if you have a performance mind for your build, I think its easier to stay with the 85/86. Of course, if that '84 is a good deal... pick it up anyway.

I know on the atvs I have worked on, some people have lightened parts or clutch discs that can be used to increase speed. Do the gyros have anything that can help that clutch? Maybe springs that engage better.

Never seen any aftermarket TG50 Gyro specific springs, but one could always experiment. Springs won't make top end speed, but might put the engine in a better position of the powerband as the clutch engages.

Have you tried doing port work or larger carbs on the gyro?

No on cyl porting, have cleaned up the intake some. But since cyls are not easily found, I'm planning to follow a tip from the Jenning book here, and start by trimming a piston top. Nothing so far has me past 31-33mph, and that includes having tried an Elite 50 domed piston. Don't let my lack of progress stop you. I'm not working hard on the speed end.

maddog · Post by **maddog** » Thu Dec 11, 2008 8:03 pm

the gyro & spree are both a joke when it comes to building them up according to the engine shops i deal with, and you guys get your parts from us

mousewheels · Post by **mousewheels** » Thu Dec 11, 2008 11:20 pm

the gyro & spree are both a joke when it comes to building them up according to the engine shops i deal with, and you guys get your parts from us

Yes, the Gyro will never be running in the fast pack. Personally just faster than the other guys Gyro will be fine

scooterwerx · Post by **scooterwerx** » Thu Dec 11, 2008 11:22 pm

whats the saying? dont have to be faster than the bear, just faster than the other people hes after?

Twilight · Post by **Twilight** » Thu Dec 11, 2008 11:32 pm

mousewheels wrote:Twilight,
I'll get photos for the Gyro cyl tomorrow - was busy tonight...

Here's reply to your earlier comments.

There's a freewheeling clutch inside the trans, not all of it has to rotate when coasting, it's loafing ;^). Rear tires at recommened 11psi are poor rolling resistance. And though low, the Gyro position is likely no better than a tuck on the dropped bars of a bicycle.
I found that overinflating gives it some fun drift and also a good 1mph speed gain today. Did a 360 in works parking lot.

Anyway - 2mm would get us around 55cc. There's import pistons on eBay International for the Honda Vision that should work. The seller has 2mm overbores - ask for part 935058. This item number is for a std 310084860330. I've got a pair of these - but been sitting for 1 1/2 years :^( Here's some links to an older threads for oversize pistons from other sources on this board. http://www.hondaspree.net/phpBB2/viewto ... c&start=15 http://www.hondaspree.net/phpBB2/viewto ... 18&start=0
2mm would be best, that way there is still 1 bore size. Every 4000 miles the piston and rings should be replaced I reckon by past experience. I'll try eBay and that seller and see what I can get.

The '84 engine should bolt up to the pivot mount. But there's little differences. First gear ratio is lower on the '85/86. Port timing is different, with the '85/86 opening sooner and longer. Internally, the clutches are different too. The '84 have more mass, I think they engage sooner. The brake cable bosses are different, the '85 are larger diameter, your cables won't fit up correctly with an '84 engine. There's some bolt thread differences for the bolts that mount the exhaust and a few other minor items. So if you have a performance mind for your build, I think its easier to stay with the 85/86. Of course, if that '84 is a good deal... pick it up anyway.
Have you tried a 85? Today with my tires fully filler, full tank of gas, backpack with about 30 pounds I hit 34 on flat ground and 35 on hills or over 35. Tried with the 86, didnt go past 34 downhill or 31 on flat. Doesnt make sense to me...

Never seen any aftermarket TG50 Gyro specific springs, but one could always experiment. Springs won't make top end speed, but might put the engine in a better position of the powerband as the clutch engages.
Im hoping for a better shift for uphills and take offs.. It will be a test and tune.

No on cyl porting, have cleaned up the intake some. But since cyls are not easily found, I'm planning to follow a tip from the Jenning book here, and start by trimming a piston top. Nothing so far has me past 31-33mph, and that includes having tried an Elite 50 domed piston. Don't let my lack of progress stop you. I'm not working hard on the speed end.

Doing the carbon cleaning on exhaust, putting straight gas with no oil for 1min of idle and 20sec of full blast to clean out. New trans oil and a hotter plug. My 85 is not able to do hills at 28-29 and flats at almost 34 at times. My 86 that has more compression I did the same gets a good 25 on hills and 33 on the flats. I still dont get that, I dont think anything changed. I know that my black one has 140psi and the red one has 155psi. Odd. A top end rebuild with a domed piston that is cleaned and sanded, and a cylinder with exhaust and intake porting should hopefully get a better response and speed.

One member in Japan on youtube told me a Honda spree motor is a good drop in with minor work and big bores and will make a gyro 84-86 fly. I am trying to find a cylinder that has 2 head bolts like the gyro, but i think im outta luck on that.

mousewheels · Post by **mousewheels** » Thu Dec 11, 2008 11:33 pm

I am hoping that mousewheels has some pics of the cylinder so I can see how much there is to work with and if its worth it.

First pic - comparison of Spree/Gyro/Aero cyls. Exhaust ports are all different. Spree also has a smaller head bolt spacing. Exhaust port interference with the Aero cyl likely prohibits use of an Aero Big Bore kit.

Second pic: Cylinder Top views.

Third/Fourth/Fifth pics - Close ups of cyl bottoms

Note: The Gyro cases don't have clearance to let the Spree and Aero cyls drop in. Not off by much, but that's confirmed by the walls being thinner at the base of the Gyro cyl.

Note2: Interesting how Honda was increasing the size of port passages from the Spree/Gyro/Aero. Anyone here put an Aero cyl into a Spree? Guess it would take some work to adjust for the cyl bolt spacing. Aw, I suppose just putting in the Aero powertrain is easier...

Twilight · Post by **Twilight** » Thu Dec 11, 2008 11:42 pm

Mouse... you just gave me a great idea on what to do. Do you have a pic of the engine with no pivot? I have a plan but need a design to go off of.

The aero cylinder looks close. I wonder id I can machine the bottom end just enough to let it in? Would the head bolts be close or no? The exhaust can always be bent/cut and tuned for optimum performance.

my last resort is a pit engine

Kenny_McCormic · Post by **Kenny_McCormic** » Fri Dec 12, 2008 3:52 pm

A good machine shop makes anything possible...

Twilight · Post by **Twilight** » Fri Dec 12, 2008 4:24 pm

I am the machine shop, haha and the welder

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Honda Gyro TG50M (1985)...lets make her faster?

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