Rebuilding 350cc for performance. Need advice.

[cpu77]

Ok I got my hands on a 350cc engine that needs rings. So I decided to do a High Performance build. Can anyone help with Machining specs ect?

So far this is what I know
1..50mm Piston Assembly
2.High Powered Cam Shaft Can this Cam be used on the 350cc?
3.I could use a 295cc Head or have the block machined down? How much do I take down?
4.Advance the timing how do I do that? I spoke with Alpha Carts and he mentioned grinding the timing key down a bit. Anyone done this?
5.So what else can I do? /Larger Carb Jet?


I am modding my clutch to compliment these changes as well.

[ruredy]

You know it's not hard to get power from this engine, the problem is that the igniter has a built in rev limiter. So no matter how much horse power you get out of this engine it will still limit the rpm's and in turn limit its speed. No matter if you have 11hp or 111hp. your cart is still only going to run in the mid 20 mph range (depending on tires) without changing the rear end gear.
Because it is limited in the rpms you don't really need huge carbs, open exhaust, big cams, all these things may add power to the engine but how are you going to use all that extra power. The best mod for a 350 is to install a 295 head on it. This bumps up the compression quite a bit which means more horse power. This will put the 350 right up there with the smaller vtwins use in these swaps you see so much about. The problem then is the rev limiter.

[cpu77]

Jon,
THanks for all the great info!

What do people do put a standalone electronic ignition on? Putting a 295cc head on should be the same or not as good as milling the factory 350cc head correct? Whats max RPMS of the motor?

[todwil]

Jon is right the best performance upgrade is the 295 head!!!
the 295 head is a closed chambered as opposed to the 350
which is an open chambered designed

[cpu77]

Todwil,
Thats the explanation I wanted. So I will use my 295cc head! I wonder if I can mill the block a nudge to get a bit more compression out of it?

So that settles that 295cc head. What else? I can't believe there is not any threads about this. I will only have about $400 in what we have dicussed so far. I may gwt 15-17hp That seems like a bargain compared to a vtwin swap(No where near the torque I would guess though.)

[todwil]

Like Jon said the next hurdle is the ING box it has a rev limiter built in
some people have told me and I really dont know if this is true that if
you can find ING box off a '91 EZGO 4 cycle that this year and only this
year that it did not have the limiter

[cpu77]

I will go over and see if that is true tommorrow I am right next to a ezgo dealer:)

[scottyb]

A friend did this and yes you need a '91 igniter. You do not need any milling to increase compression, you will need to run high octane fuel....Compression is extreeme. you will want a little cam and some jets and a fuel pump. Good Luck

[ruredy]

They did make igniters with no rev limiters in 91 and 92. not sure how hard it is to find one but i'm guessing they're getting few and far between. I've even heard of people using msd ignition stuff but have never talked to anyone that has done that. I had decided that making a stock cart/engine run with vtwins was to costly cause of the gear change thing. Parts are pretty high for the robin engine so for all the money, time, and parts you put into one you could get a briggs which can tach a grand more than the robin engine even without a rev kit.

[cpu77]

You guys are making me doubt my $400 upgrade:) From many I talk to 15-16hp should be very easy from a 350cc. If I only spend $400 that comes out to $60-$70 a hp (Remeber I have a 9hp).

Here is my calculation (New HP=15) Minus (old 295cc 9hp Engine)=6hp Devided buy cost of project ($400)=$60-$70per HP

The cheapest big block kit is 18hp $1800. So my cost per hp is $200! Not sure what my stock 295cc engine and clutch is worth so maybe I am missing a angle. I am trying to be frugal (NOT What I usally do)! The 23hp kit is actually a better deal $ for HP wise about $146 per additional HP.

All this said it is no doubt a vtwin is a much better engine. More torque/Higher stock rev/Better aftermarket/just more options! I just am trying not to drop $2100 on a engine swap right now. I want to do a posi rear end, high speed gears and new suspension first:) Does the robins engin use a magnetic pickup for RPM?