he did warm up the engine but still, after a few mins of racing the lean bog issues would come up, and the engine is not even hot, immediately after he replaced the needle he said that there was a big change in the performance, ran the engine for 15 straight mins (1 refill) and not a single lean bog after the needle change.

Was at an open practice today. I had probably 5 really experienced guys trying to help me tune my 3 port R.

I fouled two O.S. P7's and one P3.

We tuned it rich, we tuned it lean, we tuned it just right. It wouldn't hold the tune over the course of a tank. I'd pull it in and park it on the box and go do my marshalling. Come back and it'd need to be re-tuned. It takes forever for the bottom end to load up, as well. We'd tune it rich, warm it up for several minutes, then throw it on the track. A few laps into it the throttle would do weird things. Kind of like a wobbling sound. Everyone said lean bog, so we'd be richening it to the point that the motor would almost choke up and flame out but it still happened. It also fouled 3 plugs as stated earlier. Fouled them at all different fuel:air mixtures.

Temps were around 175 all day.

What in this motor is causing tuning wonkiness and fouled plugs? $35 dollars worth of plugs adds up really fast.

Was the element on your plugs destroyed.....like it was mashed up inside the plug?

It sounds like your running too fat on the bottom and too lean on the top....also....how many shims are under the head button?

I am running an '08 model 3R and haven't had any of these issues.

I don't think he has tuning issues, he said experienced guys tried many tuning options, I think he has a problem with his carb, I could be wrong though.

I'm not saying there's no way it could be the carb. Is it an '08 or '07 model?

That should help figure it out.

well thank you for the heads up dint know that using this eng. means to study at go technology school for tunning engines WOW! bog issues? plugs? pipes? fuel? temp? so many yet when we run an os ..novarossi...rb.... i guess its not that hard thank you mugenb46 ,sachoppers,djballen,zjatorad...etc.. as of now i find it a head ache!....... but still here is what i can use for the r-spec...plugs p3,p4,p6,p7....novarossi plug 5tcf up to 7tcf,,,,,,,pipe go 2047,os 2050,2060,jp3,jp4,hong-nor 053, 2047,2062...novarossi,9901,9886....do you think i need more

Had the exact same issues today with my 3 port R as the guy described below. Two very experienced tuners got it running amazingly. Let it sit for about an hour (no change in outside temp during this time) and it suddenly has about 65% top end speed and very erratic behavior. What could it be that is making it lose its tune like this? Air leaks, the carb? I'm still very new at this, but the people at my track are not and its even got them stumped.

I recently been having the same issue with my 5 port. It was running fine the day before still a little rich since I only had about 3/4 of a gallon through it. The next day I couldn't get it to hold a tune. Once I got it to idle decent, the engine would lean bog. I richend up the HSN until it was sticking out pass flush. I finally returned the needles to factory break-in settings and started over trying to tune. What needles are people using to help correct this issue? I don't want to spend $70.00 to $80.00 on an OS carb. The whole reason I bought this engine was for its cost and performance. Any help with what seems to be a lean bog issue will be appreciated. Thanks

The elements all look excellent, the plugs look great. They're just dead.


How do I tell which year it is? It was bought in... April. The head is called "coral". The carb is black and the case is metallic. Hope this helps.


Hmmm. Just pulled my head off, burn room off and it appears that there is just one shim, the aluminum one. I will add that I've never changed the amount of shims on this engine. This is how it was shipped to me. I would have expected a lot more shimming. And I was under the impression that Go's were one aluminum shim and two copper or brass shims?

yes, if you only have 1 alum shim there arew shimms missing, out of the box they should have 1 alum, 1 thick and 1 thin, plus the breakin shim in the box, i normally don't use them on the 3 ports.

I'll add, I actually had one of the Canadian Go Tech dealers helping me tune. He looked at my fouled plug and said it looked fine. Tested it and confirmed it was dead. He even tuned the engine a little differently than other people had earlier on in the day. He raised my idle and I put in several laps, brought it in, marshalled, came back and it dropped the tune. Lots of people said they thought I still had it really rich.

i have also had some 3 ports come in with the back plate screwes a little lose, it's always a good idea to double check the head bolts and back plate, the very first 3R i got was back firing and running very inconsistant, i removed the breakin shim and reset the carb, i always apply preasure to the top of the carb so the o ring is tight against the case.

Brian is like a ninja....

When you say you dont use them on 3p...you mean you dont use any shims?
and with what fuel%.?:

He means he doesn't always use the extra break in shim. You always have to have shims...just not the extra one.