Two stroke tuning help ???
Discussion
I have been reading the other threads on two stroke engines on air fuel mix,
I’m running a 50hp two stroke outboard which is water cooled around the bores. So my question is if I lean the mix to much would it seize too??
Also i heard you can tune your engine by the spark plugs
What would I be looking for?
My engine has had all the work I can do within my race rules skim the head different reeds got to keep my limiter on which cuts in at 8,500rpm not suppose to polish ports ….. but may have had a little.
Would love to hear any tuning suggestions
I’m running a 50hp two stroke outboard which is water cooled around the bores. So my question is if I lean the mix to much would it seize too??
Also i heard you can tune your engine by the spark plugs
What would I be looking for?
My engine has had all the work I can do within my race rules skim the head different reeds got to keep my limiter on which cuts in at 8,500rpm not suppose to polish ports ….. but may have had a little.
Would love to hear any tuning suggestions
Even with water cooling it'll seize if you weaken it off too much.
Getting the CR up & remaking the squish is critical, measure the squish to piston clearance using a piece of solder through the plug 'ole.
After that you need to make sure that the transfer ports line up crankcase to barrel & the transition is smooth. It's worth buying A Graham-Bell book on 2 stroke tuning, still the best!
http://www.amazon.co.uk/Two-stroke-Performance-Tun...
Getting the CR up & remaking the squish is critical, measure the squish to piston clearance using a piece of solder through the plug 'ole.
After that you need to make sure that the transfer ports line up crankcase to barrel & the transition is smooth. It's worth buying A Graham-Bell book on 2 stroke tuning, still the best!
http://www.amazon.co.uk/Two-stroke-Performance-Tun...
tr7v8 said:
Even with water cooling it'll seize if you weaken it off too much.
Getting the CR up & remaking the squish is critical, measure the squish to piston clearance using a piece of solder through the plug 'ole.
After that you need to make sure that the transfer ports line up crankcase to barrel & the transition is smooth. It's worth buying A Graham-Bell book on 2 stroke tuning, still the best!
http://www.amazon.co.uk/Two-stroke-Performance-Tun...
Blimey we used that book 20 years ago to tune my TS50 - all bang on though; Line up the ports, make the exhaust port slightly wider and move the roof up slightly. We even made a complete exhaust system following all the formulas for an expansion chamber - I remember writing the programs in BASIC... lol..Getting the CR up & remaking the squish is critical, measure the squish to piston clearance using a piece of solder through the plug 'ole.
After that you need to make sure that the transfer ports line up crankcase to barrel & the transition is smooth. It's worth buying A Graham-Bell book on 2 stroke tuning, still the best!
http://www.amazon.co.uk/Two-stroke-Performance-Tun...
There are some very good two stroke tuning guides from Lodgemark Press - they have done most of the guides that Kart racers use.
If you are going to run a two stroke to the limit my advice would be to start pre-mixing the fuel & oil to do it accurately.
There are a lot of opinions on how much oil to use. I have heard people say 16:1 95RON
il up to 50:1 using Castrol A747. My opinion is that 20:1 is about right on something being given some serious stick, and use Castrol R30 in the winter, R40 in the summer.
I'd be very interested to know what the engine is and if you can post a few photos that would be nice.
Also is the cooling system using lake water or is it closed?
Where in the UK are you based too?
If you are going to run a two stroke to the limit my advice would be to start pre-mixing the fuel & oil to do it accurately.
There are a lot of opinions on how much oil to use. I have heard people say 16:1 95RON
il up to 50:1 using Castrol A747. My opinion is that 20:1 is about right on something being given some serious stick, and use Castrol R30 in the winter, R40 in the summer.I'd be very interested to know what the engine is and if you can post a few photos that would be nice.
Also is the cooling system using lake water or is it closed?
Where in the UK are you based too?
As said the squish band clearance is all important, .040" is typical but still huge. You could probably halve that. Plug tuning has to main points to consider. looking at the earth electrode you will see where it's got an annealed appearance. The further up the plug the hot spot has gone the hotter the plug has been running and vice verca. As for mixture, you're looking inside the plug for the corona ring and the colour of it. What you don't want to see on your plugs are any specks of aluminium or flecking.
Go to lean on fuel and you'll get detonation near the exhaust port which will be the cause of seizure. I'd stay on the rich side at WOT.
Oh, raising the ports can increase top end power. You can add a thicker gasket under the barrel and a thinner gasket under the head. Or run without a head gasket after ensuring the surfaces are flat.
What engine is it?
Go to lean on fuel and you'll get detonation near the exhaust port which will be the cause of seizure. I'd stay on the rich side at WOT.
Oh, raising the ports can increase top end power. You can add a thicker gasket under the barrel and a thinner gasket under the head. Or run without a head gasket after ensuring the surfaces are flat.
What engine is it?
Edited by Boosted LS1 on Tuesday 30th December 21:44
tr7v8 said:
GavinPearson said:
Also is the cooling system using lake water or is it closed?
/quote]
Gavin, all outboards are raw water cooled, don't know of one that uses a closed loop. The bigger better ones run thermostats & some sort of bypass to keep the temps within limits.
OK. That's less than desirable, mainly because you'll lose heat transfer capability and increase the risk of detonation./quote]
Gavin, all outboards are raw water cooled, don't know of one that uses a closed loop. The bigger better ones run thermostats & some sort of bypass to keep the temps within limits.
If the engine is aluminium you should clean the cooling passages with hydrochloric acid. In the US we have a brand of toilet cleaner called "Lysol" - which is basically hydrochloric acid and a detergent. That works fabulously at cleaning the inside of blocks and heads and is very cheap ($3/bottle). If you can convert to a closed loop system you will keep the engine cooler & help it last longer (lake water has no corrosion inhibitors so it will just corrode the engine from the inside out) & use a conventional silicated coolant.
GavinPearson said:
There are some very good two stroke tuning guides from Lodgemark Press - they have done most of the guides that Kart racers use.
If you are going to run a two stroke to the limit my advice would be to start pre-mixing the fuel & oil to do it accurately.
There are a lot of opinions on how much oil to use. I have heard people say 16:1 95RONil up to 50:1 using Castrol A747. My opinion is that 20:1 is about right on something being given some serious stick, and use Castrol R30 in the winter, R40 in the summer.
I'd be very interested to know what the engine is and if you can post a few photos that would be nice.
Also is the cooling system using lake water or is it closed?
Where in the UK are you based too?
Hey ya I’m in Southampton, I thought Id ask about mixing oil too as we have to pre mix and it is at 50:1 so should lean it up a bit? We use the best stuff rock oil have as they sponsor us. If you are going to run a two stroke to the limit my advice would be to start pre-mixing the fuel & oil to do it accurately.
There are a lot of opinions on how much oil to use. I have heard people say 16:1 95RON
il up to 50:1 using Castrol A747. My opinion is that 20:1 is about right on something being given some serious stick, and use Castrol R30 in the winter, R40 in the summer.I'd be very interested to know what the engine is and if you can post a few photos that would be nice.
Also is the cooling system using lake water or is it closed?
Where in the UK are you based too?
It’s a 50hp Tohatsu 750 cc which we run in salt water comes up though the leg around the bores and exhaust them dumped back into the sea
ill get a few pic’s of the engine tonight
Boosted LS1 said:
Oh, raising the ports can increase top end power.
Always at the expense of low-mid torque though. If you have a tuned exhaust the shape of the roof of the exhaust port can make a difference as well, a very flat roof provides the fastest opening and strongest pressure wave in the exhaust, at the expense of ring life and noise.Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff