35HP Vanguard Mods?

[Hollywoodc]

Hi Guys, First post on the forum.
I hope Im not shunned on this forum for not actually having a 6x6, but I came across the 6x6 world by researching mods for my 35 Vanguard on a Minibuggy project I've built. The only other guys running the big block engines are Mud boaters but they run different RPM's and setups which don't really apply to the same type of performance That Im going for.

Although, After doing the research and going through the Springer videos, I think I got the 6x6 bug and have been doing the Daily search on CL for possible 6x6 deals! I think a 6x6 would be a great budget build for my GF and her son. So after Im done with this Minibuggy project, I think I might tackle a 6x6.

But for now, I want to try and get this 35hp Vanguard to its peak performance with what I can afford for the meantime. So Im any advice or insight would be greatly appreciated and hopefully others may be able to take some of the info for their own use.

So here is what Im working with and what I have accomplished so far. I think Im almost there but I do have some questions to get me to the next level.

The buggy started off as a Chinese Joyner/Roketa 250cc chassis which already had a 35HP Vanguard with a Forward/Neutral/Reverse Transfer case. The Chassis had a crashed front end and Instead of replacing broken parts and still only having 6-8 inches of travel, I decided to go for a full Long travel conversion.

This is how it started.


This is what it ended up looking like. 15 inches of Travel front and back.


With the Stock engine, Max speed through the whoops was about 30-35MPH WOT. Does good through the dunes but have to drive strategically and cut it short while climbing the dunes because lack of power. I'd cut it halfway up while my buddies in their RZR's would fly by.

[Hollywoodc]

So The Mods began with whatever I could find good deals on and whatever I could make on my on.
Found a Pair of Older Mikuni VM40 Carbs for $100. Im only going to run a single Carb but its nice to have an extra for spares. I measured the inside of the Carb at the throat and its actually closer to 38mm then 40mm.
Gave all the parts a good 30 minute soak in Boiling Lemon juice for a good cleaning.
Went to Sudco to pick up some rebuild parts and a few jets to get started with. I really have no idea of where to start with the Jets so this is what Im starting off with.

Pilot: 40
Main Jet: 240
Im thinking I should be more around 30 and 175 on the Jets

Its missing the Air Jet, but I was told that it wasn't needed with this setup.


Picked up some Mandrel bent tubing for the Header and got a good deal on an Akrapovic Carbon Fiber Exhaust Can that I shortened about 5 inches. Header Tubing 1.5-2.375






I removed all the stock Linkage and made a Governor shaft lock.

[Hollywoodc]

Next was the Carb Intake.
I tried to make it as short as possible so that the Filter wouldn't be too close to the header. I picked up a Uni fliter for an ATC 350x and prefilter sock. I still need to make an adapter for the filter to angle it up away from the header heat along with a heat shield.

[Hollywoodc]

The only problem I had while test running the engine was that the Round Slide was getting stuck from the amount of Vacuum going into the engine. I searched and searched about this problem and even tried swapping Slides. I found info on the Motorcycle Norton and BSA forums whom had the same problem using VM carbs. Must be something with the Intake dimensions. But I found a heavier spring that I cut down to fit and replaced the stock Mikuni return spring and it worked out great!
You can hear the way the engine sounds and the RPM's getting stuck in this video.
I still have to make a new video of how the engine sounds once I get it dialed in a bit.

http://youtu.be/kHMBLl0trHA

[Hollywoodc]

I have yet to know what the RPM's are and or what they are hitting with the mods.
So I picked up a 2" Tach from harbor Freight. That will be the next step is hooking it up but I have yet to take off the Flywheel cover and see what Im working with or how hard it will be to adapt the tach.


I spoke to Al Hodge from Performance V-Twin, whom I have to say was Very Helpful and a Great guy. He is sending me some New Valve Shims to solve the High RPM Float problem with the Valve springs. He suggested 8 .060 Shims, but to start with 4 and then check the with the gauge, if needed then use all 8.

As you can see I don't have a large budget so Im doing what I can with what I have. Once I get it fully running, then I'll look into a Cam and I will fully remove the Governor Shaft. Al Also suggested new Valves because the stock is a 2 piece and they have a tendency to come apart, but he said Its mainly a reassurance mod because if they do come apart then it ruins the engine.

[Hollywoodc]

So, To the questions:

My first question is, will I need a Rev Limiter or should I just wait and see what kind of numbers I pulling first?

Second, Timing Key. I've been told that I should adjust the Timing key and I have seen them being sold on sites but I think I can make one myself. Im just not sure how to go about adding the timing key or am I just using the key as a tool?

Any Tips or insight would be greatly appreciated.
Im hoping that I can transfer all this info and mods to a 6x6 build in the future.

[Tomo]

HI
The big blocks are similar in modification compared to the small blocks .The conrods and valve train do not like to be reved . Upto 5500 rpm a few stock items can be used but over this all will need replacing . Eg 600 racing [bando engine] s/block used stock valves then they found the heads falling off so they include a new exhaust valve now . There rpm limit is 5600 .
A 36 mukuni with an adjustable accelerator pump will work better for accelerating 4 stroke than the vm series or twin 33 with accel/pump
The chance of over reving is high so a rev limiter or tacho is needed
A tacho that is electronic/ programmable eg for DIS-distributorless ign system ,,2-4 stroke ,,1-12 cylinders with pick up of the no1 cylinder plug wire --EQUIS---

tomo

[Nubs]

The round slides will stick open and you'll have your hands full with tryin' to shut it down at the worst time. a 35hp just pulls to much vacuum. that's why most bike's run the dual cable setup that assures the slide is pulled back shut. a 40mm is about as small as ya can go on a 1000cc's IMO

[Nubs]

Here's what a little to much valve float will get ya



Al makes rods for the 35, given time you'll be needin' them, well, if your left foot works like mine does anyways

[Hollywoodc]

Thanks guys for the quick responses.

So until I can get a Rev Limiter put in, what should I keep the Max RPM range at 5000?
The Mud boat guys have Rev Limiters that go from 4200-4600. That sounds kinda low to me.

As For the Carb, With the new spring setup, I have yet to feel it get stuck while testing it around the parking lot. I understand why they would use an HSR carb with a Push Pull to keep this problem from happening or go with a larger 42 carb.

Would it be beneficial if I took the carb to my friends machine shop and Bored it out to a 42mm or a true 40mm?

Those Rods look mighty nice and Might Pricey! Do you think I will have a problem with just adding the shims to the stock valve springs?
Al said to start off with .060 shim, then check so they are within .030 gap. If still not enough then to add another .060 shim.

[Tomo]

hi ,
Which size carby does Al use for the big block ??. His comment for the small block is that he only uses the non pump carb was due to pricing . The tm pump carbs are a little pricey . The benefit is very good throttle response way better than any non pump carby . A pumper carb is mechanically connected to your foot but a non pumper is only vacumn sensing reaction so therefore changes in fuel metering are slow . The use of a single 36mm would be the smallest carb I would use but there are 4 things at play here
1 / it is not a high reving engine
2 / does not have highly efficient cylinder heads
3/ having the largest carburetor is only good for one part of the rev range
4/ the buggy is heavier than a motor bike, torque is equally as important as WOT hp

tomo

[Nubs]

[Nubs]

Well I guess i'll answer the timing key question. the key is just a guide/tool, many builders over the yrs don't even use a key. the keys sold are nothing more than a notched stock part. the most important thing is to mate the flywheel to the shaft using valve lapping compound. you can install the key into the shaft and scribe a line at the base and remove it and just cut 1/2 the width of the key down to the scribe line. you will gain about 3 degrees of advanced timing but its always best to check it before and after with a timing light. install the key with the notch to the left and install the flywheel and rotate it clockwise t'il you feel it hit the key.
Don't waste Your money on the rev limiter, use your tach as your guide
Al builds engines for a living and it would be crazy for him to give away all His tricks over the phone IMO. a 1000cc's is volume and you need to have enough carb to supply it, ignition and cam timing/lift, jetting etc will determine your full range of torque but others may have a different view

[Hollywoodc]

Awesome, Thanks Guys.

I'll keep all the factors and insight in mind.

I'm still waiting for the Shims so I wan't be working on it until I get those in.
I'll keep you posted.

[Tomo]

hi
The advice Al gives is comprehensive and details specifically to the vanguard engine .This just shortens your test and tune /dyno time . Tuning is all about where u want the hp/torque to occur . Specific to application . By using the largest or all the smallest spec items almost guarantees a less than desirable outcome . A vanguard engine typically has restricted cylinder heads and to a lesser degree the inlet manifold [depending on rev limit ] The camshaft has to have a lot more duration to try to rev the engine . Even the lifter design /size has an effect compromising the profile of cam shaft . A rev limiter and preferably a multi stage unit is used more so for engine protection and sometimes as a no look tacho guide . Considering a vanguard with shims under the valve springs only extends the rpm limit a small amount and tolerates little or no over rev an engine saving device will be a good investment . Gearing and cvt setup influences this also .To not understand how a complete engine/chassis/ vehicle package works and in what application seriously compromises an outcome.

tomo