Porting GT 750. I ask the help!!!

[v.f.]

All hello! There is a desire to modify cylinders for driving along the street with rare departures on races, but the basic driving on a city. There is a desire to receive 80-85 bhp on a back wheel. Cylinders 76 years to lift exhaust port above 35mm it will not turn out, as I wish to establish reeds valve and 36 mikuni. The forum has already studied, but anything suitable has not found. The most suitable variant http://www.ozebook.com/compendium/tr750/tune/tune3.htm" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;
But it is not clear what to do with transfer port??? I spread measurements of the cylinders, I will be grateful for any help. Thanks!

[tz375]

80HP is possible without change to the transfer ports if you fit a spacer below the cylinder to raise it. That will raise the exhausts, transfers and intakes. You can then lower the exhaust port floor and transfer floor but do not lower the intake floor. You can raise the roof of the intakes to clear the piston at TDC but that is not crucial because there is very little flow through the intake at TDC.

You have to machine as much off the top of the barrel as you add with spacer and second gasket.

Raising the exhaust roof with a spacer helps mid range to top end power 5,500- 8,000. Raising transfers with a spacer helps teh same. Raising the intake floor (spacer) helps low end power <5,000.

You can raise the exhaust by porting but don't go too far. Intake and exhaust can both be widened but be careful on the intake ports. It is very easy to make them too wide ad the piston skirt does not close the port very well.

2.5mm to 3.0mm is a thick enough spacer. Order from COMETIC in the US or through a COMETIC dealer for export.

Fit good pipes and you should get 80hp with stock carbs. and more with VM34 carbs.

Increase compression for more low end power and fit a good electronic ignition.

[v.f.]

80HP is possible without change to the transfer ports if you fit a spacer below the cylinder to raise it. That will raise the exhausts, transfers and intakes. You can then lower the exhaust port floor and transfer floor but do not lower the intake floor. You can raise the roof of the intakes to clear the piston at TDC but that is not crucial because there is very little flow through the intake at TDC.

You have to machine as much off the top of the barrel as you add with spacer and second gasket.

Raising the exhaust roof with a spacer helps mid range to top end power 5,500- 8,000. Raising transfers with a spacer helps teh same. Raising the intake floor (spacer) helps low end power <5,000.

You can raise the exhaust by porting but don't go too far. Intake and exhaust can both be widened but be careful on the intake ports. It is very easy to make them too wide ad the piston skirt does not close the port very well.

2.5mm to 3.0mm is a thick enough spacer. Order from COMETIC in the US or through a COMETIC dealer for export.

Fit good pipes and you should get 80hp with stock carbs. and more with VM34 carbs.

Increase compression for more low end power and fit a good electronic ignition.

Well! I mean I do porting, as here http://www.ozebook.com/compendium/tr750/tune/tune3.htm" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;
Not touching transfer ports, I remove from the block of cylinders 2.5мм and to a treasure base gasket 2.5 mm? Or to remove from the block 3 mm, and base gasket to put 2.5мм? Yes! Jemсo pipes too should be bought?
I am sorry, but this translator.....

[v.f.]

Yes! Concerning increase in degree of compression how you consider on how many it is possible to cut cylinder head? Electronic ignition? I think to establish ignition and CDI from yamaha xs850, I think that it should be not worse than what I saw on the Internet))) has found one more variant porting, what you think in this occasion?

[v.f.]

80HP is possible without change to the transfer ports if you fit a spacer below the cylinder to raise it. That will raise the exhausts, transfers and intakes. You can then lower the exhaust port floor and transfer floor but do not lower the intake floor. You can raise the roof of the intakes to clear the piston at TDC but that is not crucial because there is very little flow through the intake at TDC.

You have to machine as much off the top of the barrel as you add with spacer and second gasket.

Raising the exhaust roof with a spacer helps mid range to top end power 5,500- 8,000. Raising transfers with a spacer helps teh same. Raising the intake floor (spacer) helps low end power <5,000.

You can raise the exhaust by porting but don't go too far. Intake and exhaust can both be widened but be careful on the intake ports. It is very easy to make them too wide ad the piston skirt does not close the port very well.

2.5mm to 3.0mm is a thick enough spacer. Order from COMETIC in the US or through a COMETIC dealer for export.

Fit good pipes and you should get 80hp with stock carbs. and more with VM34 carbs.

Increase compression for more low end power and fit a good electronic ignition.

Thanks big!!! You say, what I can do nothing in general??? I simply cut from above the block on 3мм and to a treasure base gasket 3мм and all?! I will have 80 hp? And that it is necessary to make what to receive 80 hp on cranked to a shaft? I am sorry, but this translator.......

[tz375]

Извините, но я не владеющих русским языком

That was: Sorry, but I do not speak Russian, translated by Google.

JEMCO pipes good for 75HP at rear wheel with mild porting or up to 100HP with wild race porting.

Add Spacer at bottom of block and machine the same amount off teh top to keep stock compression. Machine more off to raise compression slightly.

If you fit a spacer, widen intake and exhaust ports slightly but do not try to port it AND fit a spacer if you want to run it on the street. For racing you can port it AND add spacer.

Do NOT shorten piston skirts - that hurts power below 5000 RPM.

You can fit better VM or TM type carbs if you want. They make more power than stock BS40 CV carbs.

Good luck with the translation

[tz375]

Well! I mean I do porting, as here http://www.ozebook.com/compendium/tr750/tune/tune3.htm" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;
Not touching transfer ports, I remove from the block of cylinders 2.5мм and to a treasure base gasket 2.5 mm? Or to remove from the block 3 mm, and base gasket to put 2.5мм? Yes! Jemсo pipes too should be bought?
I am sorry, but this translator.....

Do NOT do that porting. Fit a spacer.

[v.f.]

translate google rulezzz?Сейчас попробуем Thank you for your help! Then it turns out this is not a lot konfiguratsiya.Ya brush my ports, Bevel and put a 2.5mm gasket cometis block, exhaust pipes, carburetors, and VM36 reed valve formula 600.Stepen compression increase will not, cut the piston skirt, too, will not, modified cylinder head, left and right of the combustion chamber made ​​the same as the center, left and right plugs are pryamo.Vidimo I can think of ~ 85-90 l.s.No have a question: After changing the combustion chambers in the cylinder head, ignition of all still need to show how in the manual 3.63,3.42,3.63?



Это другой переводчик
Thanks for the help! Then such configuration turns out. I will clean ports not much, I will remove facets and I will put a lining cometiс 2.5мм under the block, exhaust pipes, carburettors VM36 and reed valve formula 600. Degree of compression I will not increase, I will not cut off a piston skirt too, the block head is modified, the left and right chambers of combustion are made same as the centre, the left and right spark plugs stand directly. Probably I can think about ~85-90 h.p. But there is a question! After change of chambers of combustion in a block head, ignition all the same should be exposed, how in a manual 3.63,3.42,3.63?

[tz375]

With all 3 spark plugs fitted vertically, the timing on all three should be the same as each other 3.4mm - 22 degrees

Test compression when the engine is complete. If it is over 140psi, retard the ignition slightly. Fit an electronic ignition Ignitech.cz or http://www.accent-electronic.com" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;. For high compression/high revs use 19 degrees, for street/stock compression use 20-21 degrees.

What is reed valve formula 600? Please explain or show pictures.

Please post pictures of your engine and bike. We would like to see pictures of a GT750 in your country.

[v.f.]

I think, that in our great ***** to the country, GT750 almost do not remain, in days of Soviet Union they were delivered never by dealers. Those that have brought privately, stupid pioneers have spoilt and have buried in sheds (((I has bought this engine on ebay 6 months ago what to make cafe of the racer or streetfighter.Модифицировал a head and has touched a cranked shaft, now I think what to do with the block of cylinders. Thanks you, I have already understood, that it is necessary for me. I will spread Whenever possible photos if certainly it is interesting to you)))

[v.f.]

It reed valve ski doo mach z,formula 600, Summit,MXZ

And this ignition yamaha XS850, I at first wish to try to put it

[v.f.]

Prompt if to make please what results can be such easy porting taking into account 3 mm spacer?

[tz375]

XS850 Yamaha ignition timing has an electronic advance электронные кривой заранее ? GT750 needs timing to be fixed or to retard as revolutions increase. 4 strokes advance (timing sooner) 2 strokes timing retards (timing later as revs increase).

You have to design and build a CDI for that pickup. XS850 CDI is not suitable.

[v.f.]

In block CDI yamaha the ignition advancing is also you are certainly right concerning engine characteristics suzuki, but the engine yamaha xs850 has about similar characteristics and the maximum capacity 79 hp is reached at 8500. I wish to try to put this ignition before to pay behind road aftermarket.Насколько I understand still put nobody ignition xs 850? For now you will not try - you do not learn And what you think apropos porting which I has laid out above?

[tz375]

SKi Doo/Sea Doo reed boxes and Vforce reeds = good

You need to build reed boxes and machine the cylinder block to fit them. With reed valves, add a boost port to extend one transfer port up at 55 degrees.

With 3mm spacer, lower the ports by 3mm on the lower face. Lower the intakes ONLY if you fit reeds. No reeds leave intake floor.