Author Topic: Hesitant revs below 3,000 RPM when hot.  (Read 4882 times)

Offline Bradders

  • SOHC Member
  • Posts: 215
    • View Profile
Hesitant revs below 3,000 RPM when hot.
« on: August 05, 2019, 09:30:26 AM »
Morning. Been having trouble with my 440/4 recently. Starts nicely and ticks over fine( although maybe a bit fast) but it’s very hesitant to rev below 3,000 rpm. Makes pulling away from the lights or riding in slow traffic a pain. Runs nicely otherwise. Problem only occurs when hot. Any ideas what the problem might be ? Thanks in advance.

Offline Nurse Julie

  • 1977 CB550/4 Mongrel Brat. 1974 UK 500/4 K1. Honda CD250u.
  • Grogu
  • *
  • Posts: 8205
    • View Profile
Re: Hesitant revs below 3,000 RPM when hot.
« Reply #1 on: August 06, 2019, 10:26:50 PM »
Has it always been like this or has it only started since you fettled / adjusted / changed something?
LINK TO MY EBAY PAGE. As many of you know already, I give 10% discount and do post at cost to forum members if you PM me direct.
https://www.ebay.co.uk/sch/julies9731/m.html?item=165142672569&rt=nc&_trksid=p2047675.m3561.l2562

LINK TO MY CB400/4 ENGINE STRIP / ASSESSMENT AND REBUILD...NOW COMPLETE
http://www.sohc.co.uk/index.php/topic,14049.msg112691/topicseen.html#new

Offline Rob62

  • SOHC Pro
  • Posts: 889
  • ZZR1100D9, CB750K4, RD250F, NSR250MC21, RD350YPVS
    • View Profile
Re: Hesitant revs below 3,000 RPM when hot.
« Reply #2 on: August 06, 2019, 11:34:14 PM »
You should never get into guessing...but mine would be running lean..?

Offline Bradders

  • SOHC Member
  • Posts: 215
    • View Profile
Re: Hesitant revs below 3,000 RPM when hot.
« Reply #3 on: August 07, 2019, 11:48:44 AM »
Hi Julie. It’s not always been like it, just the last 6 weeks or so. Not touched anything on it but only does it when the engine is hot.

Offline Nurse Julie

  • 1977 CB550/4 Mongrel Brat. 1974 UK 500/4 K1. Honda CD250u.
  • Grogu
  • *
  • Posts: 8205
    • View Profile
Re: Hesitant revs below 3,000 RPM when hot.
« Reply #4 on: August 07, 2019, 12:22:10 PM »
Hi Julie. It’s not always been like it, just the last 6 weeks or so. Not touched anything on it but only does it when the engine is hot.
Most strange....I would agree with Rob, sounds like a running lean issue but unless you have picked up some debris that is partially blocking the idle jets / circuits, I can't see what else would have caused it to start recently. I know a couple of weeks ago, when we had that very, very hot weather, mine didn't feel at her best when the engine got very hot through hard riding but as soon as the air temp dropped back down into the upper 20°'s she was back to her usual running spot on state. What fuel are you using, el cheapo supermarket like i do or the upmarket expensive stuff? For a start, i would put some STP in the fuel tank and see if that has any beneficial effect. If no different, check air screw settings and if no better, report back.
LINK TO MY EBAY PAGE. As many of you know already, I give 10% discount and do post at cost to forum members if you PM me direct.
https://www.ebay.co.uk/sch/julies9731/m.html?item=165142672569&rt=nc&_trksid=p2047675.m3561.l2562

LINK TO MY CB400/4 ENGINE STRIP / ASSESSMENT AND REBUILD...NOW COMPLETE
http://www.sohc.co.uk/index.php/topic,14049.msg112691/topicseen.html#new

Offline Bradders

  • SOHC Member
  • Posts: 215
    • View Profile
Re: Hesitant revs below 3,000 RPM when hot.
« Reply #5 on: August 07, 2019, 12:32:30 PM »
Thanks Julie. I normally get petrol from my local Shell garage in Sandhurst. When you say STP is that the same as Redex? I have just put another shot of Redex in, hopefully that will sort it. Seems odd why it only happens at low revs ?

Offline ka-ja

  • ken
  • SOHC Pro
  • Posts: 736
  • yoshi 460
    • View Profile
Re: Hesitant revs below 3,000 RPM when hot.
« Reply #6 on: August 07, 2019, 12:37:25 PM »
Redex tends to be a cleaning agent, stp a lubricating agent, used to build up cranks using stp.
nice bike,nothing in the bank

Offline Nurse Julie

  • 1977 CB550/4 Mongrel Brat. 1974 UK 500/4 K1. Honda CD250u.
  • Grogu
  • *
  • Posts: 8205
    • View Profile
Re: Hesitant revs below 3,000 RPM when hot.
« Reply #7 on: August 07, 2019, 12:38:13 PM »
Thanks Julie. I normally get petrol from my local Shell garage in Sandhurst. When you say STP is that the same as Redex? I have just put another shot of Redex in, hopefully that will sort it. Seems odd why it only happens at low revs ?
Sorry, yes Redex. Only at low revs suggests idle jets if you haven't moved the air screw settings. Is the throttle cable tensioned properly?
LINK TO MY EBAY PAGE. As many of you know already, I give 10% discount and do post at cost to forum members if you PM me direct.
https://www.ebay.co.uk/sch/julies9731/m.html?item=165142672569&rt=nc&_trksid=p2047675.m3561.l2562

LINK TO MY CB400/4 ENGINE STRIP / ASSESSMENT AND REBUILD...NOW COMPLETE
http://www.sohc.co.uk/index.php/topic,14049.msg112691/topicseen.html#new

Offline Nurse Julie

  • 1977 CB550/4 Mongrel Brat. 1974 UK 500/4 K1. Honda CD250u.
  • Grogu
  • *
  • Posts: 8205
    • View Profile
Re: Hesitant revs below 3,000 RPM when hot.
« Reply #8 on: August 07, 2019, 12:39:53 PM »
Redex tends to be a cleaning agent, stp a lubricating agent, used to build up cranks using stp.
Agree, that me getting me additives confused. I have never used STP on anything 🤣🤣🤣
LINK TO MY EBAY PAGE. As many of you know already, I give 10% discount and do post at cost to forum members if you PM me direct.
https://www.ebay.co.uk/sch/julies9731/m.html?item=165142672569&rt=nc&_trksid=p2047675.m3561.l2562

LINK TO MY CB400/4 ENGINE STRIP / ASSESSMENT AND REBUILD...NOW COMPLETE
http://www.sohc.co.uk/index.php/topic,14049.msg112691/topicseen.html#new

Offline paul G

  • SOHC Master
  • Posts: 1748
  • No room left in the garage what now !
    • View Profile
Re: Hesitant revs below 3,000 RPM when hot.
« Reply #9 on: August 07, 2019, 12:57:39 PM »
Redex tends to be a cleaning agent, stp a lubricating agent, used to build up cranks using stp.
Agree, that me getting me additives confused. I have never used STP on anything 🤣🤣🤣
Now it's hesitant and smokes ;) ;)
« Last Edit: August 07, 2019, 01:51:32 PM by paul G »
Honda CB400 4
Honda CB550 K3 (sold)
Honda CB750 UK K1
Kawasaki Z650 C2
Kawasaki Z650 cafe racer (Sold)
Honda CD175 sloper

Offline ka-ja

  • ken
  • SOHC Pro
  • Posts: 736
  • yoshi 460
    • View Profile
Re: Hesitant revs below 3,000 RPM when hot.
« Reply #10 on: August 07, 2019, 02:47:40 PM »
"Agree, that me getting me additives confused. I have never used STP on anything"

   Not to worry, it is great for building up machinery and engines as it does not squeeze out or wash away, but it is hell on earth anywhere in a "wet clutch" engine, slippery stuff!
nice bike,nothing in the bank

Offline Bradders

  • SOHC Member
  • Posts: 215
    • View Profile
Re: Hesitant revs below 3,000 RPM when hot.
« Reply #11 on: August 07, 2019, 04:04:36 PM »
Is adjusting the air screws an easy job to do? Or is it best left to someone who knows what they are doing? ( not me 😀)

Offline Nurse Julie

  • 1977 CB550/4 Mongrel Brat. 1974 UK 500/4 K1. Honda CD250u.
  • Grogu
  • *
  • Posts: 8205
    • View Profile
Re: Hesitant revs below 3,000 RPM when hot.
« Reply #12 on: August 07, 2019, 04:25:12 PM »
Is adjusting the air screws an easy job to do? Or is it best left to someone who knows what they are doing? ( not me 😀)
It is a very simple procedure....this thread tells all. Thus was talking about a CB350/4 but 400/4's are the same.
http://www.sohc.co.uk/index.php/topic,19585.0.html
« Last Edit: August 07, 2019, 04:27:15 PM by Nurse Julie »
LINK TO MY EBAY PAGE. As many of you know already, I give 10% discount and do post at cost to forum members if you PM me direct.
https://www.ebay.co.uk/sch/julies9731/m.html?item=165142672569&rt=nc&_trksid=p2047675.m3561.l2562

LINK TO MY CB400/4 ENGINE STRIP / ASSESSMENT AND REBUILD...NOW COMPLETE
http://www.sohc.co.uk/index.php/topic,14049.msg112691/topicseen.html#new

Offline Bradders

  • SOHC Member
  • Posts: 215
    • View Profile
Re: Hesitant revs below 3,000 RPM when hot.
« Reply #13 on: August 07, 2019, 04:28:42 PM »
Thanks very much Julie. Will give it a try.

Offline Northy

  • SOHC Associate
  • Posts: 57
    • View Profile
Re: Hesitant revs below 3,000 RPM when hot.
« Reply #14 on: August 09, 2019, 01:18:46 PM »
Actually could be running rich , check you plug colour and air filter first.

The air filters don't have much space around them and any slight restriction i.e.  dirty air filter seen to have huge effect on running.

Oddly just had issue with one of mine, thought the air filter was fine but would splutter at  2.5-3 k and was running rich , replace the air filter all fine.

As an side I pulled the dirty pattern filter apart. The inside of the paper/cloth had a waxy feel to it and also quite hard. So although the outside looked clean, the inner bit was causing the restriction. Its was a new filter but had been in a box for 7yrs or so,so over time had gone off, if that's possible or reacted once fitted to vapours. Had me stumped for while.   
How many is too many bikes ..... when you have no space left.

 

SimplePortal 2.3.5 © 2008-2012, SimplePortal