Pipes to viper 780

your welcome, no need to thank me. Your lucky I dont charge $3.99 a minute....LOL, just kidding!

anyways, you could do the main exh port with just a dremel,because its straight in . As far as nicasil goes, as long as you grind the port out first with either a sanding stone or carbide cutter(fine) youll be ok, just take your time, or have your buddy from before raise the main exh port for you.
The rest of the porting needs to be done with someone with the correct tools and the know how on what to modify,where to modify and the correct radius. The main exh. port will make the biggest differance along with the head set up, youll likley see 10+hp gain here with the 2 things corrected.
With a 780,those cpr pipes and good porting thru out the cylinder, these make a good solid 165hp no problem in trail form. Really get aggressive and add a ported case,some other tricks and your 172-ish hp without much effort.

You dont have the first engine that has not had the porting modified, I do lots of "tune ups" to other makers of engines all the time. It doesnt matter to me, its about getting you where you wanna be performance wise and out riding again, brand of product has nothing to do with it, its a yamaha! :2strokes:
 

780 moddified

Great post. Don its a pleasure to see you posting here again regularly. I purchased two 780 cylinders off ebay to use as spares @ $75. each. I just measured the top of the exhaust port to top of cylinder. Its 29.20mm. I'm using a Starrett depth gauge so I know the measurement is good. These cylinders look ported more than I remember with my J.Simon's cylinders. The Simons cylinders are on the sled so I cant compare. The exhaust width of these two cylinders is definitely wider. Right where the side boost ports exit the cylinder. I think I would have to port match the exhaust flanges to the cylinders if I used these. Also .061 squish? Don have you become more conservative these days? Just teasing as you set me up with .048 -.050 with a slightly increased squish angle. I think it was 14 instead of 11 degrees.
 
Mrviper: Maybe you have a set of nice cylinders who are ported to sell? I dont know any in sweden who has the experience on these BB engine. Raise the exhaust port can not be any problem but I am afried its end there.
 
viperhauck said:
Mrviper: Maybe you have a set of nice cylinders who are ported to sell? I dont know any in sweden who has the experience on these BB engine. Raise the exhaust port can not be any problem but I am afried its end there.
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Hello Henrik! Maybe this guy can help you? http://i976.photobucket.com/albums/ae245/woody_1050/PIC00669.jpg

The best thing would be to send the jugs to mr viper of course.
But the shipping cost will be a pain in the a..
 
Hey Mac, hows it goin? no, I am not going more conservative,..lol, I never have been a lets just barely do something good kinda guy.....lol! I was just merely trying to get viperhauck into it running better. Without seeing and measuring the cylinders and head set up myself, I can only get him "close" on a forum but with a sure power gain. To get all the power available I would be getting into the specs like you have, would defintiely require machine work,porting and set up time. Anytime you increase the squish angle you can go tighter, increase msv, compression ratio and not have a detonation problem.

viperhauck, no, sorry I dont have any extras to sell right now. Maybe yamalars can help you out or has a friend who could port them. I would do it for you gladly,but I cant imagine the shipping back and forth. If you find someone who can do it, I will give you a few baseline specs to set them up to. I dont normally give out specs for obvious reasons..,but, I understand your in a pickle with where your located and will be happy to help ya out and get ya up and runnin the way it should,because its a yamaha after all....... ;)!
 
Find a guy who can port is easy. Get the job done right (specs) is harder. I have talk with many different people and everyone says different. Feels that I cant trust anyone, I dont want to mess up the cylinders. But what do you want for the job IF I send the jugs to you?
 
And if you want to give me a baseline specs it would very kind. I am so disapointed on hauck, why do they send this "lowpower" kit. Before this BB kit I had ported oem cylinders with the same setup except srx heads and that engine feels stronger
 
like valin and sideshowbob have stated before, about the cylinders probably seeing no port work after boring, only leaves you w/lower port heights than before. the exh will see slightly lower height/durations than before, but the transfers and rear boost port suffer the most, w/height/duration reduction after cylinder boring, cause of the angle that they enter the cylinder. part of your power loss then, is due to the reduction of transfer time/area on your ports. also, you need to raise and widen the main exhaust port like mrviper stated, but don't forget to play w/the size of the aux exh ports, as a increase in size there will yield hp gains. just be careful to not make the bridge between the main exhaust ports and the aux exh ports too narrow, as the cylinder can crack there, causing the cylinder to bulge into the piston, causing a seizure. if you even raised the rear boost port, sec transfers, and main transfers upto stock height, you would see more hp than current. maybe w/the price reduction on hauck bb's, they now leave out port work??
 
just out of curiosity viperhauck, measure from the cylinder deck to the roof of the main transfers, secondary transfers, and the rear boost port, and please report back w/measurements.
 
Its very difficult to meausure to the main exh. beacuse its no "edge" like a oem cylinder. But with a digital caliper its somewhere between 30.5-30.8mm. And from top cylinder to the lower edge on the same port is 63.8mm
 
viperhauck said:
Its very difficult to meausure to the main exh. beacuse its no "edge" like a oem cylinder. But with a digital caliper its somewhere between 30.5-30.8mm. And from top cylinder to the lower edge on the same port is 63.8mm
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Thats ok Henrick, you have done a nice job on taking pics and providing me with info to help you, I see all I need to see with the pics. There isnt too much done to those cylinders at all, and hence along with the poor head set up is the reason why your down on power.
I would suggest for the simplicity of ease and the "biggest bang for the buck" you have someone raise the main exh. port. I will also pm you a few other specs because its really not feasable to ship those cylinders to me for the amount of time youll spend waiting on shipping back and forth. Its because of this that I am giving you specs to get you up and on the trail with a bunch more power then you have now.

I will pm you the specs for the main exh. port, and piston spec, and youll need to get these done. This will make a big change and the transfers wouldnt yield the increases as much as the areas I am going to have you modify, so just leave them as is, the motor will yield a little more low end torque with them as they are.
 
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