Low RPM Rovan 36cc

[GoneRogue]

Hey guys,

Prepare for a long paragraph So took the baja out today and the thing wouldn't start at all, so I reset the Walbro 1107 carb to defaults (1 1/4 L and 1 1/2 H) to get it to start. The engine would not start unless I applied the choke before hand and when I did start it, it almost immediately would shut off unless full throttle was applied :/ I wasn't sure what was going on so I kept it alive with throttle and slowly turned the L anti clockwise to make it more rich, this raised the idle RPM's and the things would start to move, but then if i applied throttle it would go to stand still and if I let go of the throttle the RPM increased and it wanted to race off. I didn't try to long with it out of frustration but Im not sure what to do. I have the old 997 carb that still works so might try that, I also saw that the carb was a little loose but the bolts that hold it in are locktite. If anyone knows what might be the issue lmk but I am looking forward to figuring whats wrong so it doesn't happen again XD

 

[Rep732]

1107 needle settings are not what you specified and definitely address all issues first a loose carb is a huge air leak

 

[RcJunkie13]

Hey guys,

Prepare for a long paragraph So took the baja out today and the thing wouldn't start at all, so I reset the Walbro 1107 carb to defaults (1 1/4 L and 1 1/2 H) to get it to start. The engine would not start unless I applied the choke before hand and when I did start it, it almost immediately would shut off unless full throttle was applied :/ I wasn't sure what was going on so I kept it alive with throttle and slowly turned the L anti clockwise to make it more rich, this raised the idle RPM's and the things would start to move, but then if i applied throttle it would go to stand still and if I let go of the throttle the RPM increased and it wanted to race off. I didn't try to long with it out of frustration but Im not sure what to do. I have the old 997 carb that still works so might try that, I also saw that the carb was a little loose but the bolts that hold it in are locktite. If anyone knows what might be the issue lmk but I am looking forward to figuring whats wrong so it doesn't happen again XD

Your needles are way off, it’s 1 1/4 L and 2 1/4 H
For the 36cc

 

[Rep732]

Your needles are way off, it’s 1 1/4 L and 2 1/4 H

O yea? Where did you get that from? The image is from this site and no wonder why your 5b had no top end junkie
https://www.largescaleforums.com/threads/stock-carb-settings-for-1107.23483/

 

[RcJunkie13]

O yea? Where did you get that from? The image is from this site and no wonder why your 5b had no top end junkie
https://www.largescaleforums.com/threads/stock-carb-settings-for-1107.23483/

Reset the needles just like him and had tons of problems, the 36 is different.

and my 5b has a great top end, just had to lean it a little, I was running stock settings and didn’t wanna lean during break in, was only in like 1 and a half tanks during that vid.

 

[Bizzer]

Deal with the loose carb 1st, no amount of tuning will be successful you have an air leak. Loctite doesn’t mean anything if the carb isn’t tight. Remove the bolts and retorque ensuring the carb is properly seated and leak free, then move onto tuning.

 

[Troopermaniac]

This is what I would suggest if you flood your engine. This doesn't apply with your loose carb issue just giving info on how to fix another beginner issue.

Do an engine purge. Close the valves all the way, turn the rc upside down with the sparkplug out in a CLEAN area and crank the pullstart a few times to get all the gas out. Then "I do this only on cheap engines" try to start it with the needles closed, may not start but if it does start it will idle real high before dieing out. Then tune it with the default settings.
Also check your sparkplug every now and then to see if its fouled out, I have a sparkplug tester for this. If you run 25:1 and you get lots of oil coming out of the exhaust at a good tuned idle then try 30:1 "I personally wouldn't try reducing it any further".

 

[GoneRogue]

Cheers for the responses, I did know a lot of that (I didn't notice the carb being loose until the end) other then those 36cc needle set points, that will be extremely useful. Any tips on getting the carb secure, I had an air leak issue a couple months back from a stripped isolator block but I replaced it and it was fine and now its loose again but the bolts are tight, is it just a case of re torqueing it?

 

[RcJunkie13]

Cheers for the responses, I did know a lot of that (I didn't notice the carb being loose until the end) other then those 36cc needle set points, that will be extremely useful. Any tips on getting the carb secure, I had an air leak issue a couple months back from a stripped isolator block but I replaced it and it was fine and now its loose again but the bolts are tight, is it just a case of re torqueing it?

are your bolts possibly too long?

 

[Rep732]

What type of gaskets are in between the carb and the insulator block and what type of air filter plenum are you using? Pics will help us out alot.... and @Rcjunkie a rovan 36cc sounds like witchcraft to me if it were possible don't you think engine builders would offer a 36cc?

 

[Troopermaniac]

What type of gaskets are in between the carb and the insulator block and what type of air filter plenum are you using? Pics will help us out alot.... and @Rcjunkie a rovan 36cc sounds like witchcraft to me if it were possible don't you think engine builders would offer a 36cc?

Its essentially the 32cc with +1mm bore with a +2mm crank.

 

[Rep732]

I'd be curious to see if its truly a 39mm piston

 

[Troopermaniac]

I'd be curious to see if its truly a 39mm piston

I edited my post. I had to fact check it.

Stock 32cc is 38mm bore and 28mm crank.
31.76 to be exact.
34cc is 38mm bore and 30mm crank.
34.02 to be exact.
So 36cc is 39mm bore and 30mm crank.
35.84 to be exact.

 

[Rep732]

Good lad i will like your posts with a

 

[Troopermaniac]

The 30DN 38cc engine is milled out +2mm for a 40mm bore and 30mm crank " exact 37.7cc" but has a different port design as well. It makes me wonder if its a silent beast.

 

[Rep732]

Edit.... troop we can open a thread to debate lets keep this guys thread on track.

To elaborate on the OP's issue I see a few things wrong that contribute to the issue.

1: loose carb so you must address that first

2: the correct needle settings. Since you are leaner on the needles than what a 1107 is set at and now that junkie posted what rovan wants it to be set at you don't have enough fuel and keeping it on choke is restricting air to allow the engine to run on the little fuel your giving it.

3: you have to get it running on its own with no input from you to go any further with tuning for performance

 

[Troopermaniac]

I can understand boring these out but like I said if it was worth the milling wouldn't you think the known engine builders would do so?

No because of the Nikasil plating. Its extremely toxic and usually you need large expensive machinery to do so. Even the 3rd party vendors who plate cylinders charge a minimum of $200 to even look at it.

 

[GoneRogue]

So has some time to take the carb off and the isolator block was the thing coming loose, put it back on with loctite and hoping it doesn't come loose again

 

[Polar_Bus]

No because of the Nikasil plating. Its extremely toxic and usually you need large expensive machinery to do so. Even the 3rd party vendors who plate cylinders charge a minimum of $200 to even look at it.

Nikasil plating can not be conventionally machined (boring ) . It has to be honed using a specialty diamond dressed honeing stone .

 

[GoneRogue]

So update: The car still doesn't work. The carb has been fitted tight and is not loose, however I think there is still a leak but not sure, I also noticed the exhaust was a little loose so tightened that up too. But the car still doesn't want to run. I have noticed some oil/petrol leak somewhere and I think its the isolator block, I have uploaded a few pics. I have used the setting suggested by Rovan from earlier in the thread 1 1/4L and 2 1/4H. Any help guys?