Notices
Gas Engines Questions or comments about gas engines can be posted here

JC 28 CC surging

Old 09-04-2011, 03:55 PM
  #1  
CATA
Thread Starter
 
Join Date: Jun 2003
Location: New Maryland , NB, CANADA
Posts: 37
Likes: 0
Received 0 Likes on 0 Posts
Default JC 28 CC surging

I have a JC 28 cc engine that has been running fine until recently. The engine starts and has good transition. Lately the engine will surge and sometimes tries to quit at full throttle until the engine warms up well it then runs fine on the ground. Now the surging is getting worst with the motor running poorly above 3/4 throttle. I cleaned the internal screen no improvement. Could the high end be too lean causing this problem? Ignition problem? Anyone have this problem, suggestions to fix this welcomed.

Thanks
Charles
Old 09-04-2011, 05:03 PM
  #2  
ahicks
My Feedback: (2)
 
Join Date: Aug 2008
Location: Waterford, Mi/Citrus Springs, Fl
Posts: 3,812
Received 15 Likes on 14 Posts
Default RE: JC 28 CC surging

Surging is usually lean. So yes, it could be your high speed adjustment. Have you checked the rest of you fuel intake system - like the pick up tube in the tank?
Old 09-04-2011, 06:16 PM
  #3  
skip1320
Senior Member
 
Join Date: Jun 2007
Location: Egg Harbor City, NJ
Posts: 774
Likes: 0
Received 0 Likes on 0 Posts
Default RE: JC 28 CC surging

Check for air/fuel bubble,s around all gaskets,cylinder base,CC halve,s,mine was blowing bubbles at cc halve,s a dab of rtv orange did the trick,you will se it by bumping it on compression if wet,good luck!
Old 09-04-2011, 07:13 PM
  #4  
aussiesteve
Senior Member
 
aussiesteve's Avatar
 
Join Date: Oct 2005
Location: PerthWA, AUSTRALIA
Posts: 2,924
Likes: 0
Received 0 Likes on 0 Posts
Default RE: JC 28 CC surging

All suggestions given so far are correct
If they find nothing, get yourself a carb kit (D10), a can of carb cleaner, a bottle of red blue loctite and a tube of red Silicon (I use Permatex Ultracopper). Take the carb off, Take the carb covers, needles and diaphragms off. Spray the carb very clean with the spray cleaner (Including therough the orifices) and reassemble it with the blue (or Tan) pump diaphragm. Check the reeds haven't cracked. Reassemble the reeds back on, smear a little of the selaer ont he carb mounting gasket and apply a drop of the loctite to each bolt. Tighten it all back up but do not overtighten it - if you see the "rubber" gasket / holder for the reeds squeezing out of the joint, you are too tight and wil be creating an air leak.

The carb cleaner is a very handy thing to have around - you can use it to find air leaks by spraying it (using the tube supplied with the can) on the joints while the engine is running - the note will change if you spray it at an air leak. WD 40 / CRC 5-56 also is useful for this application.
Old 09-04-2011, 07:22 PM
  #5  
skip1320
Senior Member
 
Join Date: Jun 2007
Location: Egg Harbor City, NJ
Posts: 774
Likes: 0
Received 0 Likes on 0 Posts
Default RE: JC 28 CC surging

http://www.youtube.com/watch?v=nqSGRnFdtq4 ,clean area before using rtv,this video was supposed to go to Henry,forget if i ever sent it,ran good after ,think i found it by eye,not running condition,good luck!
Old 09-04-2011, 08:32 PM
  #6  
aussiesteve
Senior Member
 
aussiesteve's Avatar
 
Join Date: Oct 2005
Location: PerthWA, AUSTRALIA
Posts: 2,924
Likes: 0
Received 0 Likes on 0 Posts
Default RE: JC 28 CC surging

Hey Skip - Yep - that sure is a leak and a half. Was it from new or close to new or did it develop it after a while? Reason I ask is I have had a couple of people contact me from various points of the globe recently with running issues on these and their issues have developed after a while - It could be another specific area for me to point them to look at.
Gotta admit, I love the European made 28cc engines that I fly now - never had any such issues with those. But that is off track for this thread.

The cleaning of the area before using the RTV that you mention - another good use for the Carb Cleaner and a scouring pad.

Old 09-04-2011, 08:34 PM
  #7  
Mr67Stang
 
Mr67Stang's Avatar
 
Join Date: Apr 2006
Location: Raeford, NC
Posts: 3,822
Likes: 0
Received 1 Like on 1 Post
Default RE: JC 28 CC surging

Just watched your video. Counter on you tube said I was the first Anyway, I assume that was fuel/oil mix in the crank case pumping out at the gasket seal of the case halves as you turned the crank by hand? Was engine surging the sympton of this leak?
Old 09-05-2011, 04:30 AM
  #8  
skip1320
Senior Member
 
Join Date: Jun 2007
Location: Egg Harbor City, NJ
Posts: 774
Likes: 0
Received 0 Likes on 0 Posts
Default RE: JC 28 CC surging

It was under half a gallon,I dont think it was runnig bad,honestly can,t remember,like I said,cleaned w/alchol and smutzed on some rtv orange,the last two owners never had a problem,ran strong,would buy a dl 30 instead now though. http://www.youtube.com/watch?v=p4xHw0E-CTw
Old 09-05-2011, 09:21 AM
  #9  
CATA
Thread Starter
 
Join Date: Jun 2003
Location: New Maryland , NB, CANADA
Posts: 37
Likes: 0
Received 0 Likes on 0 Posts
Default RE: JC 28 CC surging

Thanks for all the good advice. I checked over all the fuel system for leakes and the motor gaskets. i changed the plug and richen the high end just a little. This seemed to get rid of the high end surging. I will try this and fly it.

Thanks
Charles
Old 09-05-2011, 06:15 PM
  #10  
karolh
 
Join Date: May 2002
Location: Mandeville, JAMAICA
Posts: 6,724
Received 19 Likes on 18 Posts
Default RE: JC 28 CC surging


ORIGINAL: aussiesteve

Hey Skip - Yep - that sure is a leak and a half. Was it from new or close to new or did it develop it after a while? Reason I ask is I have had a couple of people contact me from various points of the globe recently with running issues on these and their issues have developed after a while - It could be another specific area for me to point them to look at.
Gotta admit, I love the European made 28cc engines that I fly now - never had any such issues with those. But that is off track for this thread.

The cleaning of the area before using the RTV that you mention - another good use for the Carb Cleaner and a scouring pad.

Aussiesteve,

Please tell, which 28ccc are you referring to.

Karol
Old 09-05-2011, 06:38 PM
  #11  
aussiesteve
Senior Member
 
aussiesteve's Avatar
 
Join Date: Oct 2005
Location: PerthWA, AUSTRALIA
Posts: 2,924
Likes: 0
Received 0 Likes on 0 Posts
Default RE: JC 28 CC surging

Hi karolh
The European one to which I refer is a 3W - , not everybodys cup of tea in the purchase price but worth every cent of it to me.

Charles
Let us know how it went. It is possible the engne has simply "leaned a bit" due to it running in but I have often found that when an engine tune changes quickly, something else has contributed to it.
Old 09-05-2011, 07:14 PM
  #12  
karolh
 
Join Date: May 2002
Location: Mandeville, JAMAICA
Posts: 6,724
Received 19 Likes on 18 Posts
Default RE: JC 28 CC surging


ORIGINAL: aussiesteve

Hi karolh
The European one to which I refer is a 3W - , not everybodys cup of tea in the purchase price but worth every cent of it to me.
I figured as much. I'm still kicking myself as I had the opportunity of buying a 3W 24i some time ago and made it slip by.... silly me.

Karol
Old 09-08-2011, 01:28 PM
  #13  
CATA
Thread Starter
 
Join Date: Jun 2003
Location: New Maryland , NB, CANADA
Posts: 37
Likes: 0
Received 0 Likes on 0 Posts
Default RE: JC 28 CC surging

I had a chance to fly today. The motor started fine and ran fine with only a small amout of surging on the first start. It smoothed out after it warmed up. I may still have a minor problem once the cowl is inplace so I may ritchen it a little more with the cowl on and retry.
Charles
Old 10-05-2011, 04:12 AM
  #14  
JVB
Senior Member
My Feedback: (2)
 
Join Date: Feb 2002
Location: Hastings, NE
Posts: 391
Likes: 0
Received 0 Likes on 0 Posts
Default RE: JC 28 CC surging

My JC 28 may have developed the same problem. I've been running it for a little over a year. Not a huge amount of run time, but it has run flawlessly until last weekend. Last weekend it died a couple of minutes into the flight. Tried it again with the same result. I thought it might be the ignition. Started it on the ground last night. At somewhere between 1/2 and 3/4 throttle, it was surging. If I went to wide open, it would die. I opened the high speed needle in quarter turn increments. The surging went away and it ran at WOT. I am now sitting at 3+ turns open and it doesn't seem to want to run rich. I don't know what suddenly changed, but I think it is most likely a carb issue.
Old 10-05-2011, 02:33 PM
  #15  
aussiesteve
Senior Member
 
aussiesteve's Avatar
 
Join Date: Oct 2005
Location: PerthWA, AUSTRALIA
Posts: 2,924
Likes: 0
Received 0 Likes on 0 Posts
Default RE: JC 28 CC surging

CATA
If the cowl makes a big difference to the way the engine runs, you have one of (or both) the following issues.

A - The effective Inlet area is bigger than the effective outlet area and you are building pressure in the cowl. That pressure will change depending on a few factors but especially related to airspeed. To overcome this, you may want to look at cowl entrance baffling and/or cowl exit baffles.

B - Because of pressure fluctuations in the cowl, the carb ambient pressure reference will get an incorrect reading. To correct this you may want to run a tube form the reference point (the little hole on the cover with 4 screws on it - most solder a tube in there) to a static pressure area such as the fuselage or outside the cowl via a rear facing tube.
Old 10-05-2011, 02:39 PM
  #16  
aussiesteve
Senior Member
 
aussiesteve's Avatar
 
Join Date: Oct 2005
Location: PerthWA, AUSTRALIA
Posts: 2,924
Likes: 0
Received 0 Likes on 0 Posts
Default RE: JC 28 CC surging

JVB
Something definitely changed on yours and it is more than likely something such as the carb or reeds reaching the preset hour limit. Sort that out (most likely with a carb kit) and don't worry too much about the engine not going rich even at 3 turns out.
The JC 28 has an oversized carb on it (WT805) that is used on some of the larger capacity engines. It allows the enigne to develop good top RPM (which is how too many engines are sold) but there is a cost to doing that. I have yet to see a JC 28 that will allow the high speed needle open far enough for the RPM to drop due to a rich condition (The only RPM drop I have seen was when the needle came right out - it dropped to zero).These carbs can not get adequate airflow through them for that carb to go rich on the high speed.

The sad part about it is the original carbs on them (the 793) were a good size match but due to a lowering of manufacturing cost, they were jsut too hard for the assemblers to get them working.
Old 10-05-2011, 02:51 PM
  #17  
JVB
Senior Member
My Feedback: (2)
 
Join Date: Feb 2002
Location: Hastings, NE
Posts: 391
Likes: 0
Received 0 Likes on 0 Posts
Default RE: JC 28 CC surging

Thanks AussieSteve!
Old 10-11-2011, 07:45 AM
  #18  
JVB
Senior Member
My Feedback: (2)
 
Join Date: Feb 2002
Location: Hastings, NE
Posts: 391
Likes: 0
Received 0 Likes on 0 Posts
Default RE: JC 28 CC surging

Regarding carb kit D10, is D10-WAT the correct one? That's the only one I can find. The one's I've seen don't have replacement gaskets for the carb to reed block to engine and carb to reed block. Is it ok to reuse the old ones?

Thanks.

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.