Apollo DB-36 with Nibbi PE30 installed...jetting issues....
 

I have the OHC motor on my DB-36 deluxe and finally got the Nibbi PE30 installed. Used a piece of silicone rubber turbo tubing 2" to 1.75", cut a stainless exhaust connector down, and attached a K&N to it. I removed the air box and routed the filter behind the shock. Had to cut the idle screw and spring down and re-grind the head on it because it was hitting the frame. It still is, but it doesn't get in the way so much that it causes the carb to be pushed aside, as it was.


I read some posts from various users here who have installed the PE30 on their hawks and installed a 125 main in it to begin with, assuming I'd step down. A 125 main jet with my setup is dangerously lean wide open.....if this was a two stroke, I would have rode wheelies up and down the road before it died and then found a gaping hole the in the piston(been there, done that).

...So, I moved up, and up and up and up...and it got better and better and better....now I'm at a 140 main(biggest i have), 38 pilot, and it will go WOT now without cutting out, but it doesn't pull hard at WOT...it flats out and then surges when I release the throttle slightly. I assume it is rich as can be through the range but still too lean wide open. I've done plug chops and it's mainly white/clean if I can do a WOT run but I don't have the best spot for doing it. When I check it after a 20 minute ride, it is white on top and black as night around the outside, but it runs well. (I think these iridium plugs would burn just about anything). It NEVER pops on deceleration now. I have checked for air leaks at idle, in which I have found none. Not sure how to do it at speed or under load. The only other thing I can think that may cause me to be using such a large jet is the tube/K&N filter(doesn't make a lot of sense to me). I assume a foam filter probably flows as well, if not better. I can't imagine a filter/tube and/or OHC is making that much of a difference, but maybe it is. I assumed I could use the hawk info as a base, but maybe it isn't the best idea. Also, if my fuel filter or petcock wasn't allowing enough fuel to enter the bowl, I think it would act completely different than it does. I did adjust the floats slightly to allow the bowl to fill up more because it was running out of fuel to begin with. Also, battery terminal was corroded. I cleaned that off and greased it.



I use 93 octane and NGK Iridium plug 2022. Needle clip is 3rd slot(intend to move once I get WOT jetting done). The Cadillac converter :hehe:, stock air box, and spark arrestor have been removed and battery moved to opposite side of bike. Let me know if I missed anything relevant. I'll add links for the other items I'm using below.


K&N Filter - https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
Intake Manifold - https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
Filter Tube - https://www.ebay.com/itm/1-75-to-2-45-Degree-Silicone-Reducer-Elbow-Bend-Turbo-Intercooler-Black-51mm-6/182049295447?ssPageName=STRK%3AMEBIDX%3AIT&_trksid =p2057872.m2749.l2649
15t Sprocket - https://www.ebay.com/itm/520-530-20MM-12T-13T-14T-15T-FRONT-ENGINE-SPROCKET-ATV-HONDA-YAMAHA-DIRT-BIKE/163449456913?ssPageName=STRK%3AMEBIDX%3AIT&var=462 790939741&_trksid=p2057872.m2749.l2649

All that said, should I just keep moving up in jet sizes and then move the needle down to to lean the mixture mid range or should I stop and figure out exactly where the extra air is coming from?? I'll try to post some pics if I get a chance.

Using a cg engined Hawk as a jetting reference was destined to fail. Your newer generation OHC cb clone breathes way better at high rpm than a cg engine. I have a 35 pilot and 125 main. A 128 main bogs out and almost fouls the plug. It took me quite a while to get my PE30 sorted, and once I got the pilot jet and idle mixture sorted it took several main jet changes and needle adjustments to figure out what worked best.

Thanks for the confirmation Megadan. Good thing I only used it as a starting point because of a lack of information on this particular combo. My jetting has been very similar to all of the CG hawks with the stock carb(115 main)....just seems odd to me that the jetting is so much different with this carb, but so similar with the other. So be it.

Here are a couple photos. Take it easy on me...it was my first venture into plastidipping because parts store had it on clearance for $3 a can. Muscle car green with gold/clear metallizer over it. Bolts are a pita now, they'll rip the dip right off if you aren't careful.

OH, I got it...Ill just have my wife ride on the back and spray some ether on it while I'm ripping her down the street! :lmao:



THAT would be a sight to see.

Your setup also differs from mine in two key ways. My intake between the carb and head is a lot longer, but my filter is bolted directly to the carb. Yours is shorter to the head but longer before the carb. This will actually cause a different kind of draw on the jets.

That's understood, the jetting difference just seems very drastic to me...to the point of uncertainty, which is why I'm here. I appreciate the insight.

I'll make note of the jets once I get it tuned properly, so that others will have something to go off of. Most likely will be drilling the jet out instead of spending more money.

Do you think shortening the filter tube would help the situation?

i know this is prob a little off subject but i have 2019 hawk 250. i have the 17/45 set up and have 115 main jet with stock pilot jet that comes with the mukuni carb. also did the air box mod. my bike tops out at 60 and i weigh 225. can i get it to go any faster to ride comfortably at 55 or 60? i recently realized i need to put 93 instead of 87. gonna start doing that when this tank empties. have 187 miles on it right now. also did the valve adjustments.been trying to find solutions but cant find any forums that could help.

At 187 miles you engine has not broke in yet and is still pretty tight. Let it get a few hundred miles on it and she will wake up.

Also, at stock compression, unless it is super hot and it's running at a huge load, 93 is just extra $ spent, it'll run fine on 87.

Found my petcock is dribbling fuel...replacing it today and I'll get back to testing.

I know you are still dialing in the jets, but have you noticed any performance/power improvements after installing the Nibbi?

There is a significant power increase. Almost whiskey throttled it into the back of my truck on the first ride, but I'll attribute that to my stupidity and lack of play in the throttle. I'm sure it looked funny. I'll report back when I get it tuned properly to let you know...it vibrated so badly I think it broke the mount off my gas tank because I didn't lay it over or anything like that, but I had to re-weld the mount last night. I'm pretty sure the vibration is mainly caused by the jetting condition though.