1QwkSport2.5r

Greetings, Bob! I am entertaining the idea of getting a SJ .30 or .35. However the Jett website is in dire need of updating and it only shows the .25-.40L as BSE only. Can I get a cast case SJ or are they BSE only? Are the rpm figures on the site using a Jettstream muffler?

Thanks in advance for the help & info!

bob27s

My Feedback: (19)

Hi,

Sorry for the delay, and thank you for writing.

Those are only available in BSE case as shown.

Cast case .25-35 size engines are not available. Dub has never manufactured a cast case in that size.

Similarly, the SJ-76L, and FIRE-90L engines are only availalble as BSE.

All of the specs, weights and dimensions shown are configured as you receive it with the JettStream muffler, and the prop indicated. So to your question, Yes, that is with the Jettstream muffler.

The "46" size engines as well as the side exhaust 90L are available in cast case.

Bob

1QwkSport2.5r

Thanks for the information Bob. Is the pricing on the website correct?

Thanks again.

1QwkSport2.5r

Bob? Is pricing on the website current?

bob27s

My Feedback: (19)

Abut 90% sure it is..

1QwkSport2.5r

Great. Thanks.

1QwkSport2.5r

Greetings again, Bob.

I have one question - I know Dub lists his performance figures for his engines using 15% nitro fuel. Is it necessary to break-in on 15% nitro? Does it matter if a guy switches between 5% and 15% periodically?

1QwkSport2.5r

Bob.... are you out there? Just curious about my last question regarding nitro requirements. I have my BSE .35 now, and am looking to get it broke in soon so its ready for the upcoming season... I mixed up some 15% just in case, but will it perform well on 5-10% nitro? I know it will drop some performance off with a little less nitro.. Will it handle 5% nitro okay or does it really need 10-15% to run properly? In the instructions that Dub sent with the engine it said to drop to a smaller prop on FAI fuel... I intend to run some nitro just to get a little more wiggle room on the needle. All but one of my engines requires no more than 5% nitro due to comrpession ratio; It would be cool if I could run the same fuel in all of my engines but if the BSE .35 will take too much of a hit in rpm on 5%, I'll stick to 10-15%. For my application, a 9x6 or 9x7 APC prop works best. I've used an 8x6 on my SuperTigre S29 and it ran okay, but not quite enough thrust to get my desired result.

Thanks in advance for any wisdom you have to share.

bob27s

My Feedback: (19)

hey...

sorry for the delay... I seem not to get notifications of posts in here that often.

All of the engines will run fine on lower nitro. Our friends over seas often run 0% and 5% fuel.

The key is you want to keep the rpm up where it should be, so yes, means backing off on the prop a little.

Usually the engine will not mind switching fuels. Key is not to try to stress it too much when you go to the lower nitro. If you are running at 9x7 to start with, then switch to the 9x6.

The only technical difference you might see in performance is the idle and transition. Nitro assists with both of those. But typically not a problem. You can try a few different plug temperatures and transition will be perfect.

Agian, sorry for the delay.

Bob Brassell

1QwkSport2.5r

Its quite alright, Bob. I thought about emailing you or Dub, but I wasn't in a real hurry to get my questions answered. I'll just run 15% fuel for now. I'd like to get some break-in runs done so its ready for the season, but I've been hesitant due to it being relatively cold outside lately. What is your rock bottom air temp you'd run one of these engines in at? I have an 8x6 prop on the engine and will end up using a 9x6 APC for normal use. The engine is very tight and with it being cold outside, I figured it might be a bit much to get it started even. I was going to use a hairdryer to heat the engine up beore popping it off the first time, figured this would loosen it up a little and make starting easier. I just dont want to roast the piston fit in the liner by having it too cold outside.


I'm going to use an 8x6 APC, 15% nitro 22% oil, and an old hot glow plug from my tool box. I save new plugs for after the bench runs and ready for service.

Thanks for getting back to me, Bob. I appreciate it!

-Tim

bob27s

My Feedback: (19)

Just wanted to check in ...... how did you make out with trying a few things?

1QwkSport2.5r

I waited until the temp was above 32°F and ran the engine per the instructions. I put the engine on the dash of my truck with the heat cranked and got the engine nice and toasty before I fired it up the first time. I used 15% nitro 25% oil, and a 25yr old OS #8 plug from my box that I'll swap out for the merlin the engine came with. The engine got plenty hot even in the cooler weather. I ran it today for 3 tanks of fuel at 16,500-16,700rpm, it was 38°F today.

I have (6) 7oz tanks of fuel through the engine so far on the 8x6 APC and put the 9x6 APC on it to see if it would turn 18k or better. It would not, I don't think its ready yet. 17,500rpm peak. I went about 100rpm lean of peak, so I richened 1 full turn on the needle, and shut it down to cool off.

I think runtime is about 20 minutes now, maybe a little less. The 7oz tank lasts for 4 minutes at 16,500rpm rich on the 8x6.

I will give it another few runs on the 8x6 to loosen it up a little more before I put the heavier prop on it.

Its getting easier to start though; my electric starter will get it going much better now.

1QwkSport2.5r

I got my .35 ran in pretty good, about 35 minutes runtime on it. With the intended 9x6 APC it peaks at 17,550rpm on 15% nitro. A 9x5 APC peaks at 18,500rpm. Based on the info I got with the engine, these rpm readings are normal for a new tight engine. I'm sure as the engine gets more time on it and the weather warms, the rpms will pick up.

How long can I expect the piston and liner set to last in non-abusive conditions using good fuel? Do these engines have that legendary last-forever problem that Enya and SuperTigre have? I'm not concerned, just curious.

bob27s

My Feedback: (19)

If you take care of it ...... will last a LONG time. Years.

I have a 12 year old SJ50 that runs better today than it did when 3 months old

Just avoid lean runs, take care of it ...... and it will get better over time

1QwkSport2.5r

Sounds great. Thanks Bob.

1QwkSport2.5r

I now have a little over a gallon through my BSE .35 with about 35min on the test stand. 18,200rpm on a 9x6 APC is quoted on the website as being the .35's capability. The engine was peaking around 17,600rpm on the 9x6 APC at the end of the test stand run. For awhile I put the 8x6 APC break-in prop back on it and ran it for several tanks with the needle set for 18,000rpm. (The 35min test stand run was with the 8x6) Just this past weekend I tried the 9x6 again and still about 17,600 peak. Do I keep the 9x6 on it and run it 500rpm rich for awhile or do I use the 8x6 and set it around 18k?

1QwkSport2.5r

Update: original bearings went south on me over the winter. Installed new bearings and am down on power. It's still tight and breaking in but I've never gotten it to peak over 17,600 on a 9x6 APC and 15% fuel. With new bearings, 15% nitro 20% castor fuel, and McCoy MC59 plug it peaked at 19,300 on an 8x6 APC and 17,250 on a 9x6 APC. This engine isn't going in a plane but a hydrofoil airboat so it's not unloading really... But other posts talking about the BSE .35 said a 9x5 should peak above 19,000 on the ground and mine won't hit 18k on a 9x5. I balance the blades and the prop hub and my fuel is made fresh by me. The website says all engines are test run to advertised power ratings before shipment but I have a hard time believing an engine as tight as this one was when I got it would rev that high. Is the website misprinted? Regardless, I'm still impressed with the engine... Just figured after almost 2gal of fuel it would run faster than it is.

bob27s

My Feedback: (19)

Hi...

Im pretty sure the website has something between 17-18000 for rpm target. The muffler is optimized for that range. But yes some folks ran it at higher rpm on occasion.

If you had it disassembled... . Double check the sleeve alignment in the case . That we run across with people often enough But even with the 9x5 look for rpm around 17500 18000 range when slightly rich.

1QwkSport2.5r

The website says 18,200 on a 9x6 APC. Never gotten any faster than 17,600 on that prop. I'll give it another gallon of runtime on a 9x5 and see where it gets me. I still don't see how it would run up to Dub's advertised spec before shipment. I suppose if I use more synthetic oil instead of castor it might spin a bit faster, but I'm not gonna replace bearings in it every year.

The liner is exactly where it's supposed to be and the bearings are exact replacements of what was in it to start with.