Measuring Heads ?

[smoknbs]

' Yamaha's PJ's also become almost inoperable because of the outlet location when air boxes are removed. Many engines went down when owners removed airboxes and ran their sleds.'

what outlets are you referring to ? pics would help

[opsled]

When looking at the carb from the airbox side the outlet (for fuel to the carb) for the PJ system is at about 9:30 (clock hand). The fuel transfer line from the bowl of the carb attaches to it. It is not in the main air flow line through the carb and without the airbox on there is not enough vacume created to make them operate properly. The engine will run lean if jetting is not compensated to correct the issue.

opsled

PS, Don't have any pics at the moment but could get some if needed.

[smoknbs]

Ok I get it , its an operatioal property of the carb needing the proper vacuum

[Vmax540]

I noticed #'s on both of these machined heads ! The one came with a 600 kit Tyler bought and the other was on an engine that I believe was ported. Anyone see these types of #'s ?

[Bob Vehring]

Phil, I never said Yami builds junk. I think they fall in the same catagory as any other sled maker, car maker bike atv, tv set computers or anything maker. They try what they can, given what they know, and are thinking at that time
Back in the early 90's we were given a job to develop a new OHV engine for Kart racing. Several groups around the country were doing this seperatly, but pooling the info together. After 3 years of every type of testing, eliminating the weak links, re-inventinting some wheels we thought we had it together yet once it hit the market and now thousands of people were racing it, it took another 2 years of changes to finally get it right
Engineers are IMO very smart people, my kids one. They go to school and are taugh how to engineer things, that doesn't mean they have real world exspieriance in what ever they are engineering and some good ideas on paper don't always work out in real life. Heres this years example for me. I picked up a ET250, ran pretty good but I wasn't happy with the carb, It has a buterfly Keihen much like my Inviter or stock SRV but instead of a float system, has a fuel pump instead mounted where the bowl should be. Sort of like a Tillitson. Searching for info I ran into a 8 page thread either on Vintage sled or vintage sledder. Every person that had one recomended switching to a 34 slider and reported nothing but trouble with the stock carb. I made the swap and it runs perfictly across the board. I'm sure someone at Yami thought it was a good plan back in '79.
Heres my best example and it holds true back in the 60 and just as true now. We just spent 6 months listening to each manufactorer telling us how good their 2012 sleds are. Now we will spent the next 6 months listening to how many changes they made and how much better the 2013's are.

Very interesting post on oil inj. I never thought about it like that. Contrary to some things I have read, more precisely, saw advertized, but I understand the idea of varying the flow to match fuel flow with out changing ratio.
So more to the point, Its Car Show weekend again, I'm spending 10 hr days at State Fair Park here in Milw at the World Of Wheels show. Have 2 race sled and a butload of karts. I'm there till Sun night. If you got time, no better place to sit around, talk oil, drink highly over priced beer, and watch the car show girls walk by. Stop up if you can

[opsled]

Hi Bob, read your PM. Responding to it and your post here so others can see what's in me brain too.

For starters I have made my thoughts on the "lean oil" theory clear on many different sites as this subject on Yammie injection methods come up often. I'm not trying to stir up trouble and don't want to be contradictory but knowone anywhere at any time has been able to prove me wrong here. (if it happens I'll yeld) I have read Cammeron's comments from Dynotec, Tim Bender and many many others on the lean oil theory. Most if not all of the brains that believe it exists I respect greatly. These guys are good. real good and their record proves it. I'm not knocking them or anyone else on the issue. The problem for me is that the lean oil theory just doesn't hold water in my brain. All the reasons I have read (I have searched everywhere and read everything I can find on the subject) to back the lean oil theory are also reasons needed to make a fixed ratio injection system possible. Reasons of "cleaner exhaust, use less oil" are also benifits of a well calibrated and controled oil injection system so they don't offer me any proof.

Here's how I come to my conclusions.

I'll start with the Yamaha making junk comment.
It was not pointed at anyone. Just a statment of fact. Yamaha has built things that didn't work, that needed changes, that needed to be eliminated. In the past they have made any change needed to improve the product and eliminate or improve issues consumers may have in the field. For a manufacturer to run the entire inventory of a specific product through a crusher (82 SRX) to avoid problems in the field tells me something. All those sleds could have been sold and most were preordered with buyers waiting to pick them up. This tells me Yamaha wil go to almost any lenght to fix an issue that has or may occure. When you think about the fact that Yamaha started injecting oil into the fuel on all their high end sleds with the invent of the Vmax 540 and kept that system on all their liquid cooled sleds untill the day they stopped building them also tells me somethin. It worked!! I have never seen a recall or update from Yamaha in regards to the system desighn. There were a couple of rich calibrations that were updated to lean out the system on a particlar model but never a system failure or design issue that I am aware of. If there was a problem Yamaha would have fixed or changed it. They didn't. This is my reason for the Junk statment. Yamaha doesn't build juck. If they do and have issues they correct them. This system was used for over 20 years on Yamaha sleds. If it didn't work as designed it would have been changed years earlier.

The engine uses fuel at different rates at different times because of RPM and load. An oil injection system needs to be able to match the rate at which the fuel is used. RPM is taken care of in the drive system for the pump. Load is taken care of through variable rate and a control cable. Where is the mechanism to change mix ratios? and why would it be needed?? I can find no answeres.

I've run this through my head over and over for years and read everything I can find on the subject to prove one way or the other the claims of lean oil. I can'y find proff. Yanaha's track record with design issues, logic, common sense and my understanding what is needed to make an oil injection system work is what I base my opinion on.

It's all I have to work with.

opsled

PS might get up to the show this weekend. Will look ya up if I do.

[Bob Vehring]

-Don't get me wrong, your theroy certianly, at least to me makes sence, and I think you know I have many brands of sleds, but the yamis are my favorites ( i also like their keyboards but think their guitars suck)
The PM I sent this mourning were just some of the examples of the type of things I have seen written over the years. Maybe the entire variable oil thing is urban ledgend. I really don't know. When this show is over, I will have more time to look around just because now you have me thinking. I will agree that not only Yamaha but I would say all brands of oil inj. seem to be about bullet proff, really don't hear of problems.
I remove the oil system on my sleds for two very different reasons, 1, I want to get rid of all the crap under the hood, and 2, and this may sound stoopid, the kids and their friends use my sleds more then I do. With all different people using them theres one simple rule for all the sleds, put oil in the gas. I don't want to here, sorry, I thought that one was injected, no, none of the are, put oil in the gas

[opsled]

OK Bob. I hear ya. I'm not telling anyone what to do with their sleds on oil, mix, premix, stock, direct injection etc. All these methods of supplying oil to a two stroke work and whatever works best for an individual is fine by me. My only peeve is that many talk of this "lean oil" deal as fact. I have tried to prove it to myself over and over one way or the other. All I have ever been able to come up with on the issue is opinions based on nothing more than anothers opinion. Direct injection over stock works. I know this to be true so if one wants to do it that way fine. I just have a problem with opinion being stated as fact. My opinion is that many kits were installed on many sleds over the years that would have lived just as long (or longer) with the stock system. I believe that most were mislead by opinion into believing the stock system was junk. I can wrap my brain around almost anyones ideas that are true and correct and they will make sense to my. This one never has. I've tried hard to make it so but I can't get it to happen. To many unanswered questions that are contrary to logic.

Anywho back to the head thickness question.

I don't know as measuring total thickness is relevant to weather or not a head has been cut. I just measured 4 different heads I have here. One I know has been cut and three stockers.

The cut head had #'s like what was posted in Vmax540's pics. 4 didgets but stamped on the front side not on top.

It's total thickness was 1.410"

The stockers measured 1.475, 1.460 and 1.480.

That's a difference of .020 on stock uncut heads.

What matters is the cylinder face and it's relation to the dome. All the ones I measured were between .030 and .035 from the cylinder face on the head down to the start of the dome (step in the head surface). Even the cut head measured .035 but it is clear that it was redomed. It was probably a head that was damaged in a burn down then cut and redomed to bring back stock spec. (my guess)

opsled

[vmax-540]

Bob I like what you did to the head, been wanting to try that my self.. As you know the off set chamber is not the best thing for performance, if I remember right they did that to get more of the heat into the intake side of the chamber and less on the exhaust side.Let us know how it works out I would really like to try that one my self..
I have cced a lot of Vmax heads stock and for the updated porting, and I have found they very quit a bit. I had to once set up a head off set by about .010 just to get the chambers to come out the same.
Any time I do a update porting spec on one of these I follow what it says for cc's of 26.3 and not pay any attention to the just removing .3mm as I have found that most of the times you have to remove a few and sometime a lot more then just .3mm, if I could give any advise here I would say to have ALL vmax heads cced and be ready to do some plaining. I think Yamaha could of done a better job on there quality control here..

[Bob Vehring]

Jeff you don't know how much I wanted to get that done and its not too far away. I really love that sled.
Once Regan began racing, nothing else has gotten done
Theres actuly alot more work done to the engine in the race sled which started as a SRV 535 and is now 600cc's. Class rules call for Fan engine, 600 or less, Stock untouched 34 mm carbs and a single pipe. It dynos 108 with the little carbs. Theres more pictures of that project in the VooDoo Max thread of my prodjects.
BTW most of the creadit for these goes to Perry Ehrlich, not me

[vmax-540]

Bob it would be interesting to see how much HP the head alone would add, are you going to do a dyno comparison with a stock head and the one with the centered plug. If you do could you let us know how it works, as I said I have been wanting to do that for a long time and am very interested how it turns out..

[Bob Vehring]

I doubt, altho I haven't really looked hard at it but the new engine is a 600, don't remember offhand the final bore measurements but it use Rotax 670 pistons so both the O-ring set up and the dome shape of the head has been changed I know the new dome chambers were cut to match the 670 HO pistons which are different from standard 670 pistons Either way the compression alone would change with a st head so it would not be a comparison of just the location of the dome center.