All Things Moto! Dirtbike Forums

Go Back   All Things Moto! Dirtbike Forums > Dirt Bike - ATV - Suspension Forums > 2-Stroke Dirt Bike Forums > 2-Stroke Dirt Bikes - KTM

Reply
 
LinkBack Thread Tools
  #1  
Old 09-24-2016, 02:45 AM
Beginner Class
 
Join Date: Jul 2015
Last Online: 10-05-2016 03:59 AM
Location: Estonia
Posts: 15
Default KTM 360 will not rev up after top end rebuild

     

I have rebuilded the top end of an KTM 360 with the year 96. The cylinder was restored and a new one ringed piston has gone in, it used to have a two ring piston.


It will not rev up, even in neutral gear and it is also smoking pretty much. It idles also only around one minute and then it dies, I do not know, if the exhaust valve is 100% correctly adjusted, but I think, that it would still rev up to the top in neutral? The carb adjustment does not affect anything, tried to adjust the air screw, idle screw and also the needle, but these did not make any change to anything. Before the disassembly it had some idle problems but it revved up pretty good. What can cause that kind of problem, what should be the next steps what to check??
Reply With Quote
  #2  
Old 09-24-2016, 03:47 PM
ATM! Pro Class
 
Join Date: Jul 2011
Last Online: Yesterday 07:59 AM
Location: Benton, LA
Posts: 4,823
Default

I need more info to try and help.
1. What year is the bike?
2. How long have you owned it?
3. How long did the bike set while the rebuild was being done?
4. Did you do this rebuild?
5. Have you done rebuilds before?
6. Are you using fresh fuel mix?
7. What is your fuel mix ratio?

Paw Paw
Reply With Quote
  #3  
Old 09-24-2016, 11:06 PM
Beginner Class
 
Join Date: Jul 2015
Last Online: 10-05-2016 03:59 AM
Location: Estonia
Posts: 15
Default

1. What year is the bike? - 1996
2. How long have you owned it? - it is my friends bike, he has purchased it this year spring.
3. How long did the bike set while the rebuild was being done? - It sat from the spring until now in a garage.
4. Did you do this rebuild? - The owner has done it
5. Have you done rebuilds before? - The owner has not done a dirt bike 2 stroke rebuild, but he is working everyday as a car mechanic and also I have supported him as much as I know, I have done one rebuild for my 94 year CR250.
6. Are you using fresh fuel mix? - The fuel has sat there from the spring I think
7. What is your fuel mix ratio? - Need to clarify with the owner.
Reply With Quote
  #4  
Old 09-25-2016, 06:36 AM
ATM! Pro Class
 
Join Date: Jul 2011
Last Online: Yesterday 07:59 AM
Location: Benton, LA
Posts: 4,823
Default

Ok with that info I would suggest there are several issues at hand.
1. The fuel mix is very old and needs to be replaced with a fresh batch.
2. The fuel vent lines need to be cleaned as pest love to make homes in them.
3. You will need to do a compression test.
4. The carb must be removed and cleaned. I suspect you have some trash or dried fuel in the carb passages and jets. The carb needs to be cleaned by doing a good soaking and not just sprayed with carb cleaner and blowing air.
5. The fuel tank needs to be removed and cleaned and the fuel pet cock filter removed and cleaned.
6. The air filter needs to be removed, cleaned and re-oiled.

A bike can't set with old fuel in it without there being issues developing and they have to be addressed prior to it running correctly.

Paw Paw
Reply With Quote
  #5  
Old 09-26-2016, 10:44 AM
Beginner Class
 
Join Date: Jul 2015
Last Online: 10-05-2016 03:59 AM
Location: Estonia
Posts: 15
Default

1. The fuel mix is very old and needs to be replaced with a fresh batch. - No change.

2. The fuel vent lines need to be cleaned as pest love to make homes in them. - All clean.

3. You will need to do a compression test. - For sure it is not any compression related issue.

4. The carb must be removed and cleaned. I suspect you have some trash or dried fuel in the carb passages and jets. The carb needs to be cleaned by doing a good soaking and not just sprayed with carb cleaner and blowing air. - Cleaned several times.

5. The fuel tank needs to be removed and cleaned and the fuel pet cock filter removed and cleaned. - No change.

6. The air filter needs to be removed, cleaned and re-oiled. - No change.

It runs now on idle when cold, when it runs warmer, then it does not idle anymore. It seems that it runs rich, with the choke applied it runs more worse. What else? Can it be the crank seals? Ignition coil?
Reply With Quote
  #6  
Old 09-26-2016, 12:05 PM
ATM! Pro Class
 
Join Date: Jul 2011
Last Online: Yesterday 07:59 AM
Location: Benton, LA
Posts: 4,823
Default

Crank seal, float height setting, rich jetting or worn cylinder will do all of the things stated. I still think a compression test is needed as well as a leak test.
Just making the statement that the compression is good does not mean it is in fact good.
You can check the coil ohms readings on the primary and secondary sides, but that just does not sound like the problem.
Did you remove, soak and clean each part of the carb?

Paw Paw
Reply With Quote
  #7  
Old 09-27-2016, 07:05 AM
Beginner Class
 
Join Date: Jul 2015
Last Online: 10-05-2016 03:59 AM
Location: Estonia
Posts: 15
Default

Yes, the carb is soaked and cleaned properly.
float height setting - It ran good before the rebuild with the current float height setting, will try to adjust.
rich jetting - ran good before rebuilding it, is there any difference in jetting when it has a single or dual ring piston?
cylinder - the cylinder is re-plated and looked like a new one.

Last edited by raksike; 09-27-2016 at 07:14 AM.
Reply With Quote
  #8  
Old 09-27-2016, 08:55 AM
ATM! Pro Class
 
Join Date: Jul 2011
Last Online: Yesterday 07:59 AM
Location: Benton, LA
Posts: 4,823
Default

OK, what I see is that there are things you have elected to ignore and not check. These are some of the very things that will cause the issues you have ask for help with.
Float levels do change.
Compression may not be good as you think.
Things looking good without checking sizing or fit will not get this fixed.
You have to be willing to check and test things to find the problem or be ready to spend a lot of money to have a pro look at it and fix the problem.
With you not wanting to do these things , I can't help you.

Paw Paw
Reply With Quote
  #9  
Old 09-27-2016, 10:33 AM
Beginner Class
 
Join Date: Jul 2015
Last Online: 10-05-2016 03:59 AM
Location: Estonia
Posts: 15
Default

I currently do not have any tool available, to measure the compression, but I am 100% sure, that the problem is not there.

Today I have noticed one thing, when I lean the bike to the left side, then it idles good, when I lean it to the right side then it will start to sputter and wont idle.
Reply With Quote
  #10  
Old 09-27-2016, 01:05 PM
Intermediate Class
 
Join Date: Sep 2009
Last Online: 09-30-2017 12:33 AM
Location: Greece
Posts: 196
Default

PawPaw is right about the checks and you should do them, but after noticing this then probably it is the right crank oil seal or the carb float level, or even worse... worn right crank bearing which makes oil go through the oil seal but that would add some engine ticking noise for sure.
Reply With Quote
  #11  
Old 09-27-2016, 01:14 PM
Beginner Class
 
Join Date: Jul 2015
Last Online: 10-05-2016 03:59 AM
Location: Estonia
Posts: 15
Default

Changed also the crank seals today and still no difference.
I have tried to adjust the float level also but still no difference also changed one seal in the carb
Reply With Quote
  #12  
Old 09-27-2016, 01:22 PM
Intermediate Class
 
Join Date: Sep 2009
Last Online: 09-30-2017 12:33 AM
Location: Greece
Posts: 196
Default

then you should check the crank bearing for play.

when you say "tried to adjust" the float level, is it adjusted correctly within the range? if it is a Keihin PJ/PWK it should be ~16mm.
engine operation should not change when you lean the bike over at least that much as you say.
Reply With Quote
  #13  
Old 10-02-2016, 05:52 AM
Beginner Class
 
Join Date: Jul 2015
Last Online: 10-05-2016 03:59 AM
Location: Estonia
Posts: 15
Default

We got the bike running pretty good today and it idled pretty good but it smoked pretty much.
But after around 2 hours on the track the cylinder failed and the top end needs to be re-builded again



The cylinder was restored and it seems that it is damaged from the same spots where it has been welded, crap. It seized on high rpm, don`t know what to do with that bike, but I don't see anymore any point of send the cylinder to restoration for another 250eur. New cylinder is costing 630eur, maybe try to find somewhere some used cylinder? It seems that the sleeve is not replaceable, but on ebay there is one cylinder sleeve available, that`s strange.
Reply With Quote
  #14  
Old 10-09-2016, 08:32 AM
Beginner Class
 
Join Date: Oct 2016
Last Online: 12-29-2016 07:44 PM
Location: Central Oregon
Posts: 6
Default

Just about any cylinder can be sleeved. You mentioned that the cylinder was welded? Who plated your cylinder? The top end platers won’t usually work on a welded cylinder. Many times the cracked cylinders are sent to me for proper repairs, something really sounds fishy.

Backing up a few steps; is your cylinder round & straight? Who measured it for you? Most cracked & welded cylinders need an iron sleeve installed to return them to a useable condition. A sleeve adds strength & stability to the top end. I’m sorry for all of the questions but this really sounds strange. It seems like somewhere along the line that somebody botched the job someplace. Too many times it’s said that the top end was just redone; Who in the heck did the job.

How about attaching some pictures of your problem? We need to see what’s up. I’m supposed to be retired but can help when needed.

JT
Reply With Quote
Reply

  All Things Moto! Dirtbike Forums > Dirt Bike - ATV - Suspension Forums > 2-Stroke Dirt Bike Forums > 2-Stroke Dirt Bikes - KTM


Bookmarks

« KTM 200sx forks | - »
Thread Tools


Similar Threads for: KTM 360 will not rev up after top end rebuild
Thread Thread Starter Forum Replies Last Post
96 cr250 rebuild (slow rebuild) 1276brady Dirt Bike Restorations and Builds 22 01-16-2014 12:35 PM
help sourcing parts for my 500 rebuild, a no expence spared rebuild belcher69 2-Stroke Dirt Bikes - Kawasaki 0 02-07-2013 12:21 PM
Should I rebuild or not? TUK101 2-Stroke Dirt Bikes - Yamaha 6 02-13-2007 09:16 PM
My first rebuild joseph13 2-Stroke Dirt Bikes - Yamaha 8 02-02-2007 03:57 AM
Top end rebuild.... 2kHondaCR500R 2-Stroke Dirt Bike Forums 19 08-24-2004 05:43 PM


All times are GMT -6. The time now is 05:01 AM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright ©2002-2017, JDub Consulting, Inc. All Right Reserved.