Got a question for all you Go engine Guru's. I have a Gen5 5pt that is doing some strange stuff. I've been running these motors for a while now and this one has be confused. This thing has no low speed control. It's idle or wide open. One would think it was too lean but the needles are set richer than factory settings unless I am mistaken. HSN is flush which should be rich or about right. LSN is 1 turn out from flush. Got the short LSN in it. Idle gap is .9mm. I set it with the smooth side of a .035 drill bit. It will idle all day long. Run it on the track and it's wide open or idle. Blows plenty of smoke too. It's like there is a gap between idle and wide open where nothing happens. Makes it hard to work the technical areas of the track with no bottom to midrange. Any ideas besides throw an OS carb on it? Thanks.

I never thought of that, I will check the body in the morning. I will also check on my jammin with the 7 port. thanks gents. It really blew my mind when I saw that.

Question for you guys. I have a Go-Tech 21. 7pt turbo that has a bad con rod and I think possibly a bent crank.

I was thinking that I could use the con rod out of a go 28 6pt that I own and also use that crank in the 7pt. Is that possible?

I had the lowest but one ring break off in just the same way on my old gen 2 7 port..just refitted it and held it in place with a couple of blobs of JB weld..took a bit of wedging with plasticine to hold it in place while the JB set but never came off again and never caused me any problems..

good idea, thanks

If you have the short LSN then you are massively rich on the bottom end.

Long LSN will sit at around 1 turn in from flush
Short LSN will sit at around 1.75 to 2.5 in from flush normally

HSN at flush to .5 in from flush max, so your close there.

I am guessing when you gun it, it is so rich that it just bogs until the slide is open far enough to cope with the extra fuel and then it just takes off.
With a short LSN screwed that far out it is possibly not even in the spray bar at idle or low revs.
Try setting the LSN at 1.5 in from flush. This should get you running, then lean it in from there until you get a satisfactory bottom end and take off. Then fine tune the HSN a little for peak performance.

Hi All, excellent thread,
I have mm5 5 port and has done about 5 litres now, tune is pretty good except (comes off at about 115)when I come off the track the idle stays up for a bit longer than I would like, maybe about 10 seconds before it drops down,Is the low speed to rich or lean, It is the new carb were you have to tune the low speed needle.hsn is .5 in and low about 1 turn in?
Any help would be great.
Thanks

Grizz, that's what is weird about this. It does idle, it does not stutter or hesitate from idle like it's too rich on bottom. It's like there is literally a gap between idle and WOT. Imagine this, it's at idle, you move the trigger, the slide opens but it's still at idle, more trigger, still at idle, then you hit 3/4 to full throttle and then BAM, 40,000 rpm. It's very strange. I have sealed the back plate, Carb, New front Bearing, both sides of the carb pinch screw. Stock carb settings are flush LSN and 1 out on top or not? Thanks.

anyone has any reference picture of the versions of the 21 5 port motor? some I've seen has a GO on the crank and some has the R21 just want to know which vesion or which is newer

thanks

thats interesting, the only time i have seen a engine have a hair trigger like that was when the piston was in backwards. of course it wouldnt idle well then either. with this in mind i would take a look inside the engine, specifically at the piston skirt and orientation.


Without actually hearing it run and based on what you are describing it seems a possibility that the piston skirt may be damaged allowing the exhaust port to be open at tdc.

I'll double check that. It is a new P/S/R I put in and went through the break-in with. Has about 1-1/2 gal. on it now. Broke it in on a bench for 1/2 gal. ran it around for the next 1/2 gal and then tuned it to Flush on top, 1-1/2 on bottom and it ran fine for 3-4 tanks and then this problem developed. I'll break it back down and double check the piston etc.. Thanks.

Of course there is always the other option, just go flush flush and tune it again but this time tilt your head the other way. when i run into any tuning anomolies i just go back to base and start again. you say that the engine has run fine before so the tune may be it.

Well I tried to do that. Went flush and flush, but it still does it. Went 1 turn out from flush on bottom trying to get it to gurgle then clear out but it's still the same. Must be sucking air from someplace is all I can think of. Thanks.

that's what happened to my 5port yesterday, just not as dramatic. Just got done taking engine apart. was the inner seal in the crank case for the carb. And of course I am now trying to play parts locator. Looks like I will need mark from massive mods for help again. I emailed 22racer to see if he has anything but have not heard back from him. 22 if you read this I am looking for part#s or-0028 and or-0014. thanks in advance Rex.

I got a couple of them o-rings from A-main not too long ago. Might be out of stock like most of the Go parts are now. Seems like the carb neck being sealed with Silicone would take care of that anyways. Maybe not..